Chemistry - Alkali Metals

Alkali Metals Grade 1-3 4-6 7-9

Objective To be able to describe and predict the properties of elements found in Group 1 based upon their electronic configuration

Outcomes Identify how properties of the elements in Group 1 depend on the outer shell of electrons of these atoms Describe the reactions of the first three alkali metals with oxygen, chlorine and water Predict properties from the given trends down the group

Starter: 1. Which elements are found in Group 1 of the periodic table?

2. What patterns/trends do we already know about elements found in Group 1 of the periodic table 3. What is the electronic configuration of elements in this group related to their reactivity?

The Alkali metals The elements in group 1, on the left of the periodic table, are called the alkali metals. lithium

Li

sodium

Na

potassium

K

rubidium

Rb

caesium

Cs

francium

Fr

These metals are all very reactive and are rarely found in nature as pure elements.

Alkali Metals

https://www.youtube.com/watch?v=CmiitvJiCPc

TASK: Complete the questions below whilst watching the video: 1. How many electrons do group 1 metals have in their outer-most (valence) shell?

2. When these atoms lose this electron, what do the become?

3. Why are group 1 metals stored in oil?

4. What are some physical properties of group 1 metals?

5. Describe what you would observe if you dropped lithium, sodium & potassium into water 6. How would you describe the reactivity of the metals as you go down the group?

Self-assessment: 1. 1 electron in their outer-most shell.

2. If they lose this 1 electron they become ions with a +1 charge.

3. The alkali metals are stored in oil as otherwise they will react quite quickly with air, forming a layer of oxide on their surface.

4. Some physical properties of group 1 metals are that they are shiny and they are soft.

5. If you dropped lithium into water you would see it float on water, fizz and slowly disappear. Sodium reacts more vigorously with water and potassium reacts even more violently and also burns with a lilac flame.

6. As you go down the group the metals react with a lot more vigour with water.

The Alkali Metals - Reactivity

• Reactions all involve the loss of the outermost electron.

• Losing this electron seems to get easier as we go down the group.

Because the bigger the atom, the further the outer electron is away from the nucleus and so the easier it is to lose.

Reactivity Increases

• Reactivity increases down the group.

Task: Copy & complete: As As you you go godown downthe the group, group,the thereactivity reactivity increases. increases.Lithium Lithium is is the the least least reactive reactive and and potassium potassiumis is the the most mostreactive. reactive.

This This is is because because the the negative negativeelectron electron in in the the outer outershell shell is is further further away away from from the the positive positivenucleus nucleusin in potassium potassium than than in in lithium. lithium.It It is is less lessattracted attracted to to the the positive positivenucleus nucleusmeaning meaning it itcan can be be lost lostmore more easily. easily.

Word Bank : negative, positive, reactive, outer shell, attracted, most, increases, more, least

Modelling – Reaction with Water When alkalis metals react with water, hydrogen gas is produced - it makes a lighted splint go out with a squeaky pop.

When universal indicator is added to the reaction mixture, it turns purple – this shows it is alkaline.

The general word equation for this reaction is: alkali metal + water

alkali metal hydroxide + hydrogen

For lithium this would be: lithium

+

water

lithium hydroxide

+

hydrogen

Task: Complete the following equations by filling in the blanks to show the reaction of different alkali metals with water: a) Potassium + water Sodium b) ____________ + water Lithium c) ____________ + water water d) Francium + ______ Caesium + _______ water e) _________ f) Rubidium + _________ water

potassium hydroxide + ________ hydrogen hydrogen sodium hydroxide + __________ hydrogen lithium hydroxide + ___________ Francium hydroxide + hydrogen _______________ hydrogen Caesium hydroxide + ___________ Rubidium hydroxide + __________ hydrogen

Self-assessment

Task: You will be given some information about alkali metals, read through in pairs and answer the following questions: 1. What are three similar properties of all alkali metals?

2. Name two differences between the properties of alkali metals 3. Name the type compound formed and give the chemical formulae for when lithium reacts with: a) Oxygen b) Water c) Chlorine

Self-assessment: 1.

Similar properties could include: all shiny, good thermal and electrical conductors, soft to cut, kept in oil to stop them reacting with moisture or air, tarnish in air.

2.

Differences include their density, the softness of the metal increases as you go down the group, a does the reactivity of the metal.

3.

a) Lithium + oxygen b) Lithium + water c) Lithium + chlorine

Lithium oxide (Li2O) Lithium hydroxide (LiOH) + hydrogen (H2) Lithium chloride (LiCl)

Task: Complete the following equations: 1. Lithium + __________

Lithium oxide

2. ______ + _________

Sodium oxide

3. Potassium + ________

Potassium oxide

4. ______ + chlorine

Lithium chloride

5. Sodium + chlorine

___________

6. Caesium + _______

Caesium chloride

Self-assessment: Oxygen Sodium

Oxygen Oxygen

Lithium Sodium chloride

Chlorine

Plenary – True or False?

FALSE

1. Potassium is the least reactive alkali metal 2. As you go down Group 1 the elements become less reactive FALSE 3. As you go down Group 1 the elements gain more and more electron shells TRUE 4. Potassium is able to lose it’s outer electron more easily than lithium TRUE