ii Gold foil is a solid metal. How are the atoms of gold arranged in the foil?
iii What did the fact that the majority of the α-particles passed through the foil suggest about the structure of the atoms?
iv Remarkably, some of the α-particles were repelled back in the direction from which they came. What part of the structure of the atom did this suggest the particles had hit, and why were these particles repelled backwards?
b The isotopes of certain elements, such as carbon-14, can be of use in biochemical and medical research. Because they are radioactive, they can be used by scientists to track the synthesis and use of compounds important in the chemistry of cells and tissues. i
Complete the table about the isotopes of some common elements, making deductions from the information given. For each element, the second isotope is a radioisotope used in research. Isotope
Name of element
Proton number
Nucleon number p
12 6
C
14 6
C
1 1
H
3 1
H
31 15
P
32 15
P
127 53
I
131 53
I
carbon
6
12
6
Number of n e 6
6
1 hydrogen (tritium) 15
31
iodine
53
53
53
ii Researchers are able to use these radioisotopes to study the chemistry of cells because these atoms have the same chemical properties as the non-radioactive atoms. Why are the chemical properties of all isotopes of the same element identical?
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Cambridge IGCSE Chemistry
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