Handbook c6 periodic table

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Periodic Table Handbook C6

Work, look for peace and calm in work; you will find it nowhere else.

-Dmitri Mendeleev (1834-1907)

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Handbook C6 Periodic Table Note to Instructor: This ABL Handbook is only meant for students who are well versed with atomic structure, either from lessons in school, or the ABL Handbook on Atomic Structure. It will be appropriate for students of Class 10, in some regions Class, depending on the state syllabus.

OVERVIEW OF HANDBOOK ABL 1

2

3

Concept Refresher on Elements.

The need for classification, and early attempts.

Introduction to the Modern Periodic Table Trends and Periodicity

No. Of Activities 3

Time (min) 45

3

55

3 Total Time

50 150 mins

ABL WITH REFERENCE TO STANDARD S. No 1 2 3

STANDARD 9 10 10

RELEVANT ABL ABL 1 ABL 2 ABL 3

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LIST OF TABLES, CHARTS AND WORKSHEETS S.No Fig 1 Worksheet 1 Worksheet 2 Worksheet 3 Worksheet 4 Worksheet 5

Name Example of Element Card Match the Symbol to the Element Notes on Early Attempts at Classification Magic Squares Symbols Only Periodic Table Valency Worksheet

Page No 6 6 10 13 16 19

Note to Instructor: All the figures in this handbook are for the instructor’s reference only. The Charts need to be printed and shown to the students during the course of the activity. Worksheets need to be printed out in advance, and the number of worksheets required is mentioned in the Material List.

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ABL 1 Introduction to Classification of Elements ABL 1.1

Learning Objective What are the basic concepts of elements and atoms?

1.2

Why do we need to classify elements?

1.3

What were the early attempts made at classification of elements?

Key Messages Time (min) 20  An element is a substance composed of only one type of atom.  Atomic number is the number of protons in an atom.  Atomic mass is the sum of the weights of the protons and neutrons in the atom.

20  Scientists tried to classify the elements to obtain an orderly arrangement out of chaos.  Classification is always based on certain properties. 



Dobereiner and Newland both classified elements depending upon their atomic weights. Their classifications were not successful because all elements could not fit their pattern of classification.

Mendeleev created the most successful classification based on the atomic mass of elements, and called it the Periodic Table.

10

Total Time

50 min

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Time: 20 min

ABL 1.1

LEARNING OBJECTIVE: What are the basic concepts of elements and atoms?

ADVANCE PREPARATION: Material List: S.No 1

Material Worksheet-1

Quantity 1 per group

Element-Symbols Worksheet.docx

2

Elements Cards (given at the end of the handbook)

1 set per group

Things to Do: Print out 10 sets of the elements cards (please print only the first 20 elements) and 10 worksheets before the class begins.

Safety Precautions: Not Applicable Note to Instructor: The information on the Element Card is the same as you would find in a standard Periodic Table (Atomic number, Symbol, Element name, Atomic Weight.)

SESSION Link to known information/previous activity: Let us try and revise topics of the Atom and Elements that you have learnt earlier.

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Procedure: Divide the class into five or six groups.Give each group the ‘Match the Symbols to the Elements’ worksheet and ask the groups to match the symbol to the right element in five minutes or less.

Now hand out one set of the Elements Flashcards to each group. Give the learners 5 minutes to look at the cards, and then ask them the following questions.

Note to Instructor: An example of an element card is given below for your reference. Please go to the embedded document in the material list for similar cards for elements from Atomic Number 1-20.

Fig 1: Example of Elements Card

UNDERSTANDING THE ACTIVITY 1: Leading Questions: 1. How many bits of information does each card contain?

2. What are the two numbers on the cards? Do you notice any trend in these numbers?

3. What can you find out about the element from these cards?

Discussion and Explanation 1: 1. Each card contains four pieces of information- the symbol, the name of the element, and two numbers at the top and bottom of the card.

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2. The number on top is called the Atomic number. The number written at the bottom is called the Atomic Weight. You will notice that the atomic weight is usually written in decimals but the atomic number is a whole number. You would have also observed that the number which denotes the atomic weight is always larger than the atomic number.

3. You will know the name of the element, its atomic number and atomic weight by looking at these cards. But to understand this better, you must know what all these terms mean.

After you have completed Discussion and Explanation 1, you can move on to explain the following terms to your class: Chemical Symbol: The chemical symbol is usually a 1 or 2 lettered code for the element. It is usually derived from the name of the element in English or Latin. For example: Silver is called Argentum in Latin, hence its symbol is Ag. Atomic Number: The number written on top of the symbol is called the atomic number. Remember when you studied atomic structure, you learnt that the atom is made up of protons, neutrons and electrons? The protons and neutrons are inside the nucleus, while the electrons are spinning around it. The atomic number of an element is the number of protons in the nucleus of the atoms of that particular element. For example, the atomic number of Hydrogen is 1. Helium is 2, and so on.

Always remember that the number of electrons surrounding the nucleus of an atom is equal to the number of protons in its nucleus. So, the atom as a whole has no charge.

Atomic Mass: The atomic mass is the sum of the weights of the protons and neutrons in the atom. This number is written below the symbol. It is also called Atomic Weight. For example, the atomic mass of Helium is 4.0. Hydrogen is the only element which has the same atomic number and atomic mass, which is 1. This is because it has only one proton and no neutrons.

Element: An element is a substance with only one type of atom. Carbon is an element, because it contains only carbon atoms. Carbon dioxide is NOT an element, because it contains both oxygen and carbon atoms.

UNDERSTANDING THE ACTIVITY 2: Leading Questions: 1. What is the chemical symbol for Sodium and Potassium?

2. How many electrons do the following elements have: a. Beryllium b. Oxygen Agastya International Foundation. For Internal Circulation only.

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c. Argon 3. Why is the atomic mass the sum of the weights of the protons and neutrons? Why don’t we consider the weight of the electrons in the atom?

Discussion and Explanation 2: 1. The chemical symbol for Sodium is Na, which comes from its Latin name Natrium. The symbol for Potassium is K, because it is called Kalium in Latin.

2. We have learnt that the atomic number of an element is the number of protons in the nucleus of its atom. But the number of electrons surrounding the nucleus is equal to the number of protons. So we can find out the number of electrons if we know the atomic number of that particular element. The atomic number of Beryllium is 4, so it has 4 electrons. Similarly, Oxygen has 8 and Argon has 18 electrons respectively.

3. The atomic mass of an element is actually the mass of the protons, neutrons, and electrons of its atoms. However, the mass of the electron is very small (1/2000) when compared to the mass of the proton and neutron. Therefore the mass of the electron is ignored in the calculation of the atomic mass.

KEY MESSAGES:   

An element is a substance composed of only one type of atom.

Atomic number is the number of protons in an atom.

Atomic mass is the sum of the weights of the protons and neutrons in the atom.

LEARNING CHECK: What is the atomic number of: 1. Ca 2. Na 3. Al Answer for Instructor’s Reference: 1) 20, 2) 11, 3) 13

ABL 1.2

Time: 20 min

LEARNING OBJECTIVE: Why do we need to classify the elements?

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ADVANCE PREPARATION: Things to Do: Not Applicable Material List: S. No 1

Material Quantity Elements cards (From ABL 1.1) 1 per group

SESSION 1.2A Link to known information/previous activity: Since we have revised concepts of atoms and elements, let us now try to arrange the elements.

Procedure: This is a group discussion. Ask learners how many of them have visited a provision store. Tell the class to spend five minutes thinking about how a provision store has hundreds of items, and how all of them are arranged.

Leading questions: 1.

2.

3.

4.

What are the various types of things you can buy at a provision store?

How are the various things arranged in the store?

Can you think of a reason why all the items are arranged in this manner?

What would happen if we did not have a certain way of arranging the items at the store?

Discussion and Explanation: 1. You can buy almost everything you need for your household at a provision store. You can buy food grains like dal, rice, millets, cleaning agents like soaps, shampoos, detergents, snacks like biscuits, chips, mixtures and various other things.

2. The items in the provision store are all grouped together and arranged. For example, there is one shelf for soaps. In that shelf, bathing soaps are arranged in one place, and washing powders and detergents are arranged in a different place. Similarly, the shopkeeper arranges all the snacks together, there is one shelf for chips, one shelf for biscuits,etc.

3. The provisions are arranged in this way to make it easier for the customers and the shopkeeper to find things.

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4. If the items were not arranged in this order, the shop would be a complete mess and it would take very long to find the things we need.

SESSION 1.2 B Note to Instructor: The following activity allows learners to arrange the elements in any order that they want. They might arrange them according to atomic mass, or atomic number, or even alphabetically! Let the learners arrange them however they want to.

Procedure: Explain the following to your class: We have seen how provisions in a store are arranged according to what they are and what their function is.

Similarly, elements are also arranged according to some properties. If we did not have this arrangement, there would be a lot of confusion.

Now retain the groups from the first activity. Ask all the groups to take out their Elements cards. Tell the groups to discuss the best way to classify the elements, and arrange them accordingly. Give the groups about ten minutes to finish this exercise.

Now ask one member from each group to explain why they arranged the elements in the manner that they did.

After all the groups have finished their explanation, put up the Periodic Table, and ask each group to see if their arrangement matches the arrangement of the first 20 elements in the Periodic Table.

Note to Instructor: In case the class is already familiar with the Periodic Table, this will be a refresher exercise for them.

UNDERSTANDING THE ACTIVITY: Leading Questions: 1.

2.

3.

4.

What is the Periodic Table of elements?

How are elements in the Periodic Table arranged?

How many elements are there?

Can you look at some commonly occurring objects and substances around you and guess what elements they might contain? (water, sugar, salt, benches, paper)

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Discussion and Explanation: 1. The Periodic Table is a chart containing information about all the elements that make up matter.

2. In the Modern Periodic Table, elements are arranged according to their atomic number.

3. Currently, there are 118 elements known to mankind. Of these, around 98 are naturally occurring, meaning that they are found on earth as compounds. The other 20 elements are called ‘Synthetic Elements’ and have been artificially created by scientists. Elements with atomic number 99 to 118 are all synthetic elements.

4. Let us look at some common substances around us: a. Books-paper-Carbon b. Benches-wood-Carbon c. Sugar-Carbon, Hydrogen, Oxygen d. Salt-Sodium and Chloride e. Water-Hydrogen and Oxygen 5. Even though there are 118 elements, most of the things we see and use in our everyday lives, are made up of only about 20 elements! Imagine how diverse and different everything around is…but it is all made up of different combinations of the same twenty elements! Let us take the example of a language to understand this better. In the English language there are 26 alphabets, but we have so many words in English. Similarly, in Hindi, there are 47 alphabets. Think about how many words there are in a language, but all these words are different mixtures and combinations of the same letters!

KEY MESSAGES:  

Classification is always based on certain properties.

Scientists tried to classify the elements to obtain an orderly arrangement out of chaos.

LEARNING CHECK: If time permits, you can have a short quiz on elements with your class. Ask them the following questions: 1. What is the Atomic number of Calcium?

Answer for Instructor’s Reference: 20 2. Which element has an atomic number of 17?

Answer for Instructor’s Reference: Chlorine 3. The element with atomic number 13 is _________?

Answer for Instructor’s Reference: Aluminium 4. Which element has the same atomic mass and atomic number?

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Answer for Instructor’s Reference: Hydrogen.

5. What is the Atomic Number of Neon?

Answer for Instructor’s Reference: 10

TRY IT YOURSELF: Try to write your name in elements! Can you?

Example: HARISH

H

Ar

Hydrogen

Argon

I

S Iodine

Sulphur

H Hydrogen

You can also see how many words you can build using the symbols in the Periodic Table.

ABL 1.3

Time: 10 min

LEARNING OBJECTIVE: What were the early attempts made at classification of elements?

ADVANCE PREPARATION: Material List: S. No 1

Material Worksheet 2-Notes on Early Attempts at Classification

Quantity 1 print out of each note (3 in total)

Notes on Early Attempts at Classification.docx

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Not Applicable Safety Precautions: Not Applicable

SESSION Link to known information/previous activity: In the previous activity, we tried to arrange the elements. Let us now see how scientists did this many years ago.

Procedure: Explain to the class that in 1808, more than 200 years ago, John Dalton proposed his Atomic Theory. He stated that atoms of an element can be distinguished from others based on their atomic weights. After his theory came out, many scientists tried to classify elements based on their atomic weights. Tell the class that they will be learning about three such classifications today.

Divide your class into three groups. Give each Group one of the notes on ‘Early Attempts of Classification’.

Ask the learners to read and discuss the note provided to them. At the end of five minutes, one member from the group must come up and explain their note to the rest of the class. They can also show the picture of the scientist given in the note to the rest of the class.

UNDERSTANDING THE ACTIVITY: Leading Questions: 1. Who classified elements into triads? Why did this classification fail?

2. What is Newlands law of Octaves?

3. How did Mendeleev classify elements? Why was his classification the most successful one?

Discussion and Explanation: 1. Johann Wolfgang Dobereiner classified elements into triads based on their atomic weights. The atomic weight of the middle element was the roughly the average of the other two elements. His classification was not successful because he could not classify all the elements to fit this pattern.

2. Newlands’ Law of Octaves states that when the lighter elements are arranged in increasing order of their atomic weights, every 8th element has properties similar to the first one, much like notes of music. Again, he could not classify all the elements to fit this pattern.

3. Mendeleev classified elements in the form of a Periodic Table, according to their atomic weights. His classification was considered to be the most successful one because he was able to fit all elements Agastya International Foundation. For Internal Circulation only.

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known at that time into this pattern. He was even able to predict the properties of elements that were yet to be discovered.

KEY MESSAGES:  

Dobereiner and Newland both classified elements depending upon their atomic weights. Their classifications were not successful because not all elements could fit their pattern of classification.

Mendeleev created the most successful classification based on the atomic mass of elements, and called it the Periodic Table.

LEARNING CHECK: How did Mendeleev classify elements?

Answer for Instructor’s Reference: Mendeleev classified elements according to their atomic weights in the form of a Periodic Table.

How did Dalton’s Atomic Theory help in classification of the elements?

Answer for Instructor’s Reference: Dalton states that properties of elements were dependent on their atomic weights. This helped other scientists classify elements based on their atomic weights.

WEB RESOURCES: http://www.chem.msu.su/eng/misc/mendeleev/

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ABL 2 Introduction to the Modern Periodic Table ABL 2.1

Learning Objective What is the Modern Periodic Table?

2.2

Is there a link between the electronic configuration of an element and its placement in the Periodic Table?

2.3

Where are Metals and Non-Metals placed in the Periodic Table?

Key Messages  Properties of elements are a periodic function of their atomic number  The Periodic Table is classified into horizontal rows called Periods and vertical columns called Groups.  Elements in the same group have the same number of valence electrons.  Elements with the same number of occupied shells are in the same period.  The position of an element in the Periodic Table tells us about its chemical reactivity.  Metals are found on the left side of the Periodic Table, and non metals on the right.  Metalloids are elements that display properties of both metals and non metals.

Germanium and Silicon are examples of metalloids.

Total Time

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Time 20

20

15

55 min

15 Time: 20 min

ABL 2.1 LEARNING OBJECTIVE: What is the Modern Periodic Table?

ADVANCE PREPARATION: Material List: S.No 1 2

Material Large Periodic Table Magic Squares Worksheet-3

Quantity 1 per class 1 per learner

Magic SquarePeriodic Table.docx

Things to Do: Not Applicable Safety Precautions: Not Applicable

SESSION Link to known information/previous activity: Mendeleev’s periodic table was a great method of classifying the elements. But there were certain improvements made on it. Let us find out what they were.

Procedure: Put up the wall size Periodic Table chart on the wall such that it is visible to all the learners in the class. Explain the following: Mendeleev classified the elements depending upon their atomic masses. Later on, improvements were made on his classification, and the elements were arranged according to their atomic number instead; the Modern Periodic Law states that properties of elements are a periodic function of their Atomic Numbers. This new arrangement was called the Modern Periodic Table. The table is divided into 18 vertical columns called GROUPS, and 7 horizontal rows called PERIODS. The number written on top of each group is called the Group Number. The number written on the left hand side at the beginning of each period is the Period Number.

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Now hand out the Magic Squares Worksheet to all the students. Tell them that they must solve the puzzle individually. They will be given only ten minutes to complete the puzzle.

Directions for Magic Squares: Put the number of the definition from the list below the squares into the square with the appropriate term.

Check your answers by adding the numbers to see if all the sums of all rows, both across and down add up to the same number, the Magic Number.

Answer for Instructor’s Reference:

Magic Square-Solution.docx

(Adapted from www.ncclark.net)

UNDERSTANDING THE ACTIVITY: Leading Questions: 1.

2.

3.

4.

How many Groups and Periods does the modern Periodic Table have?

Can you look up Group 1 of the Periodic Table and name all the elements present in it?

Can you name all the elements in the second period?

Which period has space for elements that have been predicted but yet to be discovered?

Discussion and Explanation: 1.

2.

3.

4.

The Modern Periodic Table is divided into 18 Groups and 7 Periods.

Group 1 of the table contains Hydrogen, Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium.

The second period contains Lithium, Beryllium, Boron, Carbon, Nitrogen, Oxygen, Fluorine and Neon.

The last period, which is the 7th one, contains space for elements that are yet to be discovered.

KEY MESSAGES:  

Properties of elements are a periodic function of their atomic number.

The Periodic Table is classified into horizontal rows called Periods and vertical columns called Groups.

LEARNING CHECK: True or False.

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1. The horizontal rows in the Periodic Table are called Groups.

2. The elements yet to be discovered are placed in the 7th horizontal row.

3. The number of neutrons is called the atomic number.

Answers for Instructor’s Reference: 1. False 2. True 3. False

WEB RESOURCES: http://www.chemicool.com/

ABL 2.2

Time: 20 min

LEARNING OBJECTIVE: Is there a link between the electronic configuration of an element and its placement in the Periodic Table?

ADVANCE PREPARATION: Material List: S.No 1 2

Material Blank Sheets of paper

Quantity 1 per learner 1 per class

PeriodicTableMuted. png

3

Large size Periodic Table Pencils/pens

1 per learner

Note to Instructor: Before starting this ABL, please read ABL 1.2 on atomic structure with details of electronic configuration, etc. It will help you to explain this ABL. Things to Do: Not Applicable Safety Precautions: Not Applicable

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Link to known information/previous activity: When you studied atomic structure, you learnt to write the electronic configuration of elements. Let us see how we can use this knowledge to understand the Periodic Table better.

Procedure: Retain the Periodic Table displayed on the wall. Make sure it is visible to all learners. Divide the class into 7 teams. Provide each group with sheets of paper and pencils. When the teams are ready, assign 1 group and 1 period from the Periodic Table to the learners in that team. For example, Team 1 gets Group 1 and Period 1.

Tell the learners that you will give them ten minutes to write down the electronic configuration (ask learners to refer to their knowledge and remember their lesson on Atomic Structure where they were taught how to write the electronic configuration) of the first five elements from the group and period given to them. They can refer to the Periodic Table on display for the atomic number and names of elements.

UNDERSTANDING THE ACTIVITY: Leading Questions: 1.

2.

3.

4.

Do you see any similarity in the electronic configurations of elements within the same group?

How many valence electrons do these elements have?

Do you see any similarity in the electronic configurations of elements within the same period?

Do these elements also contain the same number of valence electrons?

Discussion and Explanation: 1. From writing down the electronic configuration of the first five elements of the group, we can see a pattern emerging. You can see that all these elements have the same number of electrons in their outermost shell. These are known as Valence Electrons. We can use elements from Group 1 as an example to explain this further.

H 1 Li 2, 1 Na 2, 8, 1 K 2, 8, 8, 1 Rb 2, 8, 18, 8, 1 From this we can see that all the elements have only 1 electron in their outermost shell. So they have only 1 valence electron. Hence, all elements within the same group have the same number of valence electrons.

2. All elements in Group 1 have 1 valence electron, Group 2 elements have 2 valence electrons, Group 3 elements have 3 valence electrons.

3. When you write down the electronic configuration of elements within the same period, you notice they all have the same number of shells. Unlike elements within the Groups, where the number of shells keeps increasing.

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Let us use elements from Period 2 as an example to understand this better.

Li 2,1 Be 2, 2 B 2, 3 C 2, 4 N 2, 5 We can see that all these elements have electrons in two shells, k and l. So, elements in the same period have the same number of shells.

4. No, elements in the same period do not have the same number of valence electrons. They only have the same number of shells.

KEY MESSAGES:   

Elements in the same group have the same number of valence electrons.

Elements with the same number of occupied shells are in the same period.

The position of an element in the Periodic Table tells us about its chemical reactivity.

LEARNING CHECK: 1. What are valence electrons?

Answer for Instructor’s Reference: Valence electrons are the electrons found in the outermost shell of an atom.

2. What are the shells around the nucleus called?

Answer for Instructor’s Reference:K, L, M, N 3. What is Electronic Configuration? Give one example?

Answer for Instructor’s Reference:Electronic Configuration is the arrangement of electrons in the shells surrounding the nucleus. For example, the electronic configuration of Sodium is 2, 8, 1.

ABL 2.3

Time: 15 min

LEARNING OBJECTIVE: Where are metals and non metals placed in the Periodic Table?

ADVANCE PREPARATION: Material List: Agastya International Foundation. For Internal Circulation only.

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S.No 1

Material Blank Periodic Worksheet-4

Quantity Table 1 per learner

Periodic table only symbols.docx

2 3

Color Pencils/Sketchpens 3 or four sets 5 chits each with names of metals, 5 for non-metals and 5 for metalloids.

Things to Do: Print the required number of worksheets in black and white. Prepare 5 chits with names of metals, 5 with names of non-metals, and 5 with names of metalloids.

Safety Precautions: Not Applicable

SESSION Link to known information/previous activity: Let us now see how the different elements are placed in the Periodic Table.

Procedure: Remove the Periodic Table that was displayed in the class for the earlier activities. Hand out the Blank Periodic Table worksheet to all the learners. Tell them that this is an individual activity and that they all must perform it on their own.

Give out the following instructions to the learners once they have all their materials ready: -Color all the metals you know in a shade of red.

-Color all the non-metals you know blue.

-If you know any elements that act like both metals and non metals, color them green.

-Use a thick black line to separate the metals from the non-metals.

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Note to the Instructor: Once the activity has been completed, please ask learners to retain their worksheets.

They will need it again for ABL 3.3.

UNDERSTANDING THE ACTIVITY: Leading Questions: 1.

2.

3.

4.

On which side of the Periodic Table do you find metals?

On which side of the Periodic Table do you find non metals?

What are metalloids?

Can you look at the elements in the third period and classify them into metals or non metals?

Discussion and Explanation: Note to Instructor: Once the learners have completed the activity, put the Periodic Table back up on display for the class to see, and explain the following.

1. Metals like Sodium and Magnesium are found on the left hand side of the Periodic Table. From the previous activity, you found out that elements in group 1 have 1 electron in their outermost shell.

From your knowledge of atomic structure, you know that for the atom to be most stable, it must lose this electron. Metals, by definition, are electron donors. So all the metals are on the left side of the Periodic Table, and the most reactive metals are in group 1 and 2.

2. Non metals like Chlorine and Sulphur are found on the right side of the Periodic Table. From the previous activity you saw that elements in group 17 had 7 valence electrons. To make their atoms stable, they need to gain an electron. Non-metals, by definition, are electron acceptors. Thus all non metals are found in the right side of the Periodic Table, with the most reactive non metals in Group 17.

Group 18 contains Noble gases, which are non reactive, as their outermost shells are already filled with 8 electrons, and their atoms are already very stable.

3. Certain elements exhibit properties of both metals and non metals, and these elements are referred to as Metalloids. Boron, Silicon and Germanium are some of the commonly known metalloids. On the Periodic Table, they are placed between the metals and non-metals.

4. The third period consists of Sodium, Magnesium, Aluminium, Silicon, Phosphorus, Sulphur , Chlorine and Argon. The first three elements in the period are metals. Silicon is a metalloid because it displays both metallic and non metallic properties. The remaining four elements are non-metals.

KEY MESSAGES:  

Metals are found on the left side of the Periodic Table, and non metals on the right.

Metalloids are elements that display properties of both metals and non metals. Germanium and Silicon are examples of metalloids.

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If time permits, at the end of the class, make 3 corners in the room- one for metals, one for nonmetals, and one for metalloids. Call 15 students and distribute the chits to them. Each chit will have the name of a metal, non-metal or metalloid. Ask learners to look at the name of the element in the chit given to them, and then go and stand in the correct corner of the room. Give them about two minutes to do this. Then learners from each group must say “I am __Magnesium__(name of element given to them) and I am a __Metal___ (Whether the element is a metal/non-metal/metalloid).

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ABL 3 - Trends in the Periodic Table ABL 3.1

Learning Objective Key Messages Time (min) How do we find the  Valency of an element is 20 Valency of an determined by the Element? Are there number of electrons any trends in valency? present in its outermost shell.  Valency remains the same while going down a group.  Valency increases and then decreases while moving from left to right in a period.

3.2

What are the trends in atomic size in the Periodic Table?



 

3.3

What are the trends in Metallic and NonMetallic Properties?







Atomic Radius is the 20 distance between the centre of the nucleus and the outermost shell.

Atomic radius decreases from left to right in a period.

Atomic radius increases while moving down a group.

Metals are 10 electropositive; they have a tendency to lose electrons.

Non-Metals are electronegative, they have a tendency to gain electrons.

Metallic character decreases across a period and increases while going down a group. .

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Time: 20 min

ABL 3.1

min

LEARNING OBJECTIVE: How do we find the Valency of an Element? Are there any trends in valency?

ADVANCE PREPARATION: Material List: S.No 1

Material Valency

Quantity Worksheet-5 1 per learner

Valency Worksheet.docx

2

Sketch pens/ color pencils

1 set per group

Things to Do: Not Applicable Safety Precautions: Not Applicable

SESSION Link to known information/previous activity: In ABL 2.2, we wrote the electronic configuration of elements. Let us use this knowledge to study another interesting concept.

Procedure: Before they begin the activity, you can refresh the learners’ memory on the concept of valency. Explain the following:

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Valency is the combining capacity of an element, and it is determined by the number of electrons in the outermost shell of the atoms in that element. You have already learnt how to calculate the valency of elements from the handbook on Atomic Structure.

Now divide the class into teams of four. Give every learner one copy of Worksheet-5, the Valency worksheet.

Assign one Group OR Period (Do NOT assign Group 18 to anyone) to each team, and ask them to find the valency of each element in that group or period. Do not assign the same Group or Period that was given to the learners in ABL 2.2. If Team 1 was given Group 1 in ABL 2.2, do not give them Group 1 again. Tell the learners they have ten minutes to complete the activity, and that you will be asking questions based on the activity once they have completed it. Even though they have been divided into teams, all the learners must individually fill out the worksheet. They can, however, discuss and take help from their team members, or divide the elements between themselves to find the valencies.

UNDERSTANDING THE ACTIVITY: Leading Questions: 1.

2.

3.

4.

5.

How do you calculate the valency of an element?

What is the valency of Calcium with atomic number 20 and Sulphur with atomic number 16?

How does the valency vary while moving from left to right across a period?

How does the valency vary while moving down a group?

What is the valency of noble gases?

Discussion and Explanation: 1. For calculating the valency of an element, we first need to know its atomic number. Let us take the example of Magnesium with atomic number 12 and Chlorine with atomic number 17. The first step to calculating valency is to write down the electronic configuration of the atom: Mg: 2, 8, 2 Cl: 2, 8, 7 From the electronic configuration, we can see that Mg has 2 electrons in its outermost shell, while Cl has 7. We know that for the atom to be stable, it must have 8 electrons in the outermost shell. For Mg to gain a stable configuration, it is easier to lose two electrons, than to gain 6. So the valency of Mg is 2. Similarly, for Cl to gain a stable configuration, it must either lose 7 electrons, or gain one electron. Since it is easier to gain 1 electron, the valency of Cl is -1.

2. The electronic configuration of Ca is 2, 8, 8, 2 and of Sulphur is 2, 8, 6. Since Ca can easily lose two electrons to become stable, its valency is +2. S, on the other hand, must gain two electrons to become stable, so its valency is -2.

3. While moving from left to right across a period, valency increases and then decreases.

4. The valency remains the same while moving down a group. This is because the number of valence electrons remain the same.

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5. We already know that Noble Gases have a stable configuration, with 8 electrons in their outermost shells. This is why noble gases have no valency or 0 valency, and are unreactive.

KEY MESSAGES:   

Valency of an element is determined by the number of electrons outermost shell.

Valency remains the same while going down a group.

Valency increases and then decreases while moving from left to right in a period.

present

in

its

LEARNING CHECK: Name 3 elements with valency 1, 2 and 3.

Answer for Instructor’s Reference: Valency 1 : Na, Li, K Valency 2: Be, Mg, Ca Valency 3: B, Al, Ga Note to Instructor: In case learners give you answers apart from these, please calculate the valency with respect to the atomic number, and check their answers yourself.

ABL 3.2

Time: 20 min min

LEARNING OBJECTIVE: What are the trends in the atomic size in the Periodic Table?

ADVANCE PREPARATION: Material List: Not Applicable Things to Do: Agastya International Foundation. For Internal Circulation only.

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Not Applicable Safety Precautions: Not Applicable

SESSION Link to known information/previous activity: We have already learnt how various elements are arranged. Let us see how their sizes vary.

Procedure: Pick around 8 students of varying heights from the class. Ask these students to come up to the front of the classroom. Make them face their classmates and stand in a horizontal line according to their height, in descending order. So the tallest learner will be on the left side, and the shortest on the right, at the end of the line. Explain to the class that the students are like atoms of elements placed in a period. Tell the learners that the atomic size decreases across a period, that is from left to right.

Now ask the learners standing at the front of the class how they would have to stand if they were representing elements in a group. They need to stand in a vertical line according to their height in ascending order, such that the shortest learner is at the beginning of the line, and the tallest at the end. Explain to the class that atomic size increases while moving down the group, that is from top to bottom of the Periodic Table.

UNDERSTANDING THE ACTIVITY: Leading Questions: 1.

2.

3.

4.

5.

Can you think of a reason why the atomic size decreases as we move from left to right across a period?

Why does atomic size increase while moving down the group?

What is atomic radius?

Now that you know the trends in atomic size, which element do you think has the largest atom?

Which element has the smallest atom?

Discussion and Explanation: 1. As we move from left to right across a period, the atomic number keeps increasing by one. We know that atomic number is the number of protons in the nucleus of the atom, so the number of protons is increasing. Because of an increase in the number of protons, the nuclear charge increases (the nuclear charge is the positive charge due to the protons, neutrons do not have any charge.) Due to this, the nucleus tends to pull the electrons closer to itself, thereby reducing the size of the atom.

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2. We have learnt from ABL 2.2 that as we move down a Group, a new shell is added to the atom.

Because the atom has an additional shell, its size will be bigger than the element placed above it in the Group.

3. Atomic radius is defined as the distance from the centre of the nucleus to the outermost shell in an isolated atom. We consider an isolated atom because if there is a group of atoms, forces of attraction between them will change the atomic size. Atomic radius is usually measured in picometres (pm). 1 pm=10-12 m.

Note To Instructor: Please refer to Handbook C5 on Atomic Structure, ABL 1.1 for table on measurements.

4. We have learnt that atomic size decreases while moving from left to right across a period. From this we can come to the conclusion that Group 1 elements would have the largest atoms. We have also seen that the atomic size increases while moving down the group. So the last element in Group1 should have the largest atom. Hence, Francium (Fr) is the element with the largest atomic radius.

5. Atomic size decreases while moving from left to right across a period, so the element with the smallest atomic radius will be on the right end of the period. Hence, Group 18 elements must be the smallest.

As atomic radius increases while moving down a group, the smallest atom must be on top of the group.

From this knowledge, we can conclude that Helium will have the smallest atom.

KEY MESSAGES:   

Atomic Radius is the distance between the centre of the nucleus and the outermost shell.

Atomic radius decreases from left to right in a period.

Atomic radius increases while moving down a group.

LEARNING CHECK: Look at the Periodic Table and answer the following.

1. Arrange the following elements in decreasing order of their atomic radius: F, O, N, Be, C, B, Li, Ne (Answer: Li, Be, B, C, N, O, F, Ne) 2. Arrange the following elements in ascending order of their atomic radius: Xe,He,Kr, Rn, Ar (Answer: He, Ne, Ar Kr, Xe, Rn)

ABL 3.3

Time: 10 min min

LEARNING OBJECTIVE: What are the trends in metallic and non metallic properties?

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ADVANCE PREPARATION: Material List: S. No 1

Material Periodic Table from ABL 2.3

Quantity worksheet 1 per learner (learners must retain the worksheet from ABL 2.3 and reuse it.)

Things to Do: Not Applicable Safety Precautions: Not Applicable

SESSION Link to known information/previous activity: Let us answer some questions looking at your worksheets from ABL 2.3.

Procedure: Ask the learners to look at their worksheet. They have already marked the metals, non-metals and metalloids in different colors. Ask them to look at their respective worksheets and answer the leading questions that follow.

UNDERSTANDING THE ACTIVITY: Leading Questions: 1.

2.

3.

4.

What happens to metallic character across a period?

What happens to non-metallic character across a period?

What happens to metallic character going down a group?

What is electropositivity?

Discussion and Explanation: 1. As you can see from your worksheets, the metals are on the left side of the Periodic Table, and the non metals on the right. This means that metallic character decreases as we move from left to right across Agastya International Foundation. For Internal Circulation only.

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a period. This is due to the fact that it is easier for elements on the right side of the table to gain electrons, rather than to lose them.

2. As we can see from the table, the non-metals are placed on the right side of the table. Non-metallic character increases across the period. Non-metals are electronegative. They have a tendency to gain electrons.

3. You have already learnt that atomic radius increases while moving down a group. The bigger the atom, the easier it is for it to lose its electrons from the outermost shell. This is why metallic character increases while going down a group.

4. Electropositivity is the tendency of an atom to lose electrons. So, metals are more electropositive than non-metals.

KEY MESSAGES:   

Metals are electropositive; they have a tendency to lose electrons.

Non-Metals are electronegative, they have a tendency to gain electrons.

Metallic character decreases across a period and increases while going down a group.

LEARNING CHECK: Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages.If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

WEB RESOURCES: https://www.teachingchannel.org/videos/periodic-table ‎

REFERENCES: 1) National Council of Educational Research and Training, Class X, November 2012.

2) National Council of Educational Research and Training, Class IX, October 2013.

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APPENDIX

Worksheet 1 Match the Symbol to the Element Name ___________________

Group________________

Match the Symbol in the left column to the element in the right.

Symbol H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca

Name of the Element Chlorine Sulphur Aluminum Silicon Magnesium Fluorine Oxygen Potassium Phosphorus Hydrogen Argon Beryllium Calcium Carbon Lithium Helium Sodium Neon Nitrogen Boron

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Worksheet 2 Note 1

Early Attempts at Classification: Dobereiner’s Triads

The first attempt towards the classification of elements was made by Johann Wofgang Dobereiner, a German chemist in 1829. He pointed out that there were sets of three elements (triads) which showed similar chemical properties. He also noted the fact that the atomic weight of the central element of the Triad was approximately the mean of the atomic weights of the other two members and the properties of the middle element were in between those of the other two members.

Dobereiner began this work in 1817, when he noticed that the atomic weight of the element Strontium, (Sr) was halfway between the wights of Calcium and Barium. He realized that these elements had similar properties, and hence he grouped them together.

Some examples of Dobereiner's Triads are : Element Atomic Element Atomic Element weight weight Li 7 Ca 40 Cl Na 23 Sr 88 Br K 39 Ba 137 I

Atomic weight 35.5 80 127

The major drawback of Dobereiner's classification was that the concept of triads could be applied to only a limited number of elements. Later, other scientists realized that there were other elements that could be grouped together, but the poor accuracy in measuring the atomic weights limited Dobereiner.

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Note 2

Early Attempts at Classification: Newlands Law of Octaves In 1865 , an English chemist, John Newlands observed that when the lighter elements are arranged in order of their increasing atomic weights, the properties of every eighth element is similar to the first one. This is much like the eighth note of a musical scale. If you have learnt music, you know the notes Sa Re Ga Ma Pa Dha Ni Sa. These are called the eight notes of music, however, the 8th note is the same as the 1st one. Similarly, in the western world, notes exist as Do Re Mi Fa So La Ti Do, and Newland was inspired by this arrangement for his classification. This classification was named as Newlands law of octaves .

Sl. No Element Sl. No Element Sl. No Element

1 Li 8 Na 15 K

2 3 Be B 9 10 Mg Al 16 Ca

4 C 11 Si

5 N 12 P

6 O 13 S

7 F 14 Cl

Sodium the eighth element is similar to Lithium, and so is the next eighth element, Potassium.

The same is true of Beryllium, Magnesium and Calcium ; Boron and Aluminium and so on. This classification was also discarded since it could not be applied to elements having atomic weights greater than that of Calcium , i.e., 40 amu. Furthermore, with the discovery of noble gases, the properties of eighth element are no longer similar to the first one.

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Note 3

Early Attempts at Classification: Mendeleev’s Periodic Table Dmitri Ivanovich Mendeleev was a Russian scientist who classified elements based on their atomic weight. He stated that properties of elements are a periodic function of their atomic weight, meaning that if the elements are arranged in increasing order of their atomic weights, their properties will be repeated.

Mendeleev’s classification is the basis for the Modern Periodic Table.

Mendeleev's classification was by far the most successful one, because along with their atomic weights, he also considered their physical and chemical properties of elements. For example, Fe, Co, and Ni were arranged together because of their similar magnetic properties.

Mendeleev started arranging elements and made this table: Cl 35.5 Br 80 I 127

K 39 Rb 85 Cs 133

Ca 40 Sr 88 Ba 137

Following this pattern, he kept adding elements in this fashion. Mendeleev's classification was also very successful because he left blank spaces for elements which were yet to be discovered. He named these elements with the name of the element it was similar to, with the prefix ‘eka-’. (Eka means ‘one’ in Sanskrit). Germanium and Gallium had not yet been discovered, but Mendeleev predicted the existence and properties of these elements long before, and named them eka-silicon and eka-aluminium !

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Worksheet-3 Name ____________________________

Periodic Table Magic Square

Directions: Put the number of the definition from the list below into the square with the appropriate term. Check your answers by adding the numbers to see if all the sums of all rows, both across and down add up to the same number, the Magic Number.

Periods

Atomic number

Symbol

_____

_____

_____

Groups

Valence

Neutron

_____

_____

_____

Electron

Mass number

Proton

_____

_____

_____

Magic Number _____ Magic number _____ Magic number _____

Magic number

Magic number

Magic number

______

_____

_____

1. positive subatomic particle 2. vertical columns on the periodic table 3. number of protons in an element 4. the electrons in the outermost energy level 5. represents an element 6. negative subatomic particle 7. horizontal rows on the periodic table 8. number of protons and neutrons 9. neutral subatomic particle

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Worksheet 4 Agastya International Foundation. For Internal Circulation only.

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Valency Worksheet-5 Name ___________________

Group/Period Assigned________________

Atomic Number Element

Electronic Configuration

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Valency