IB Chemistry SL 1.2.2 Isotopes Questions

Use isotope notation to distinguish nuclei, calculate relative atomic mass from isotope composition, and explain how nuclear differences affect physical and chemical behaviour.

Exam points

Define isotopes and read nuclear notation (Z and A) to identify the same element, isotope identity and proton/neutron relationships.
Calculate relative atomic mass or isotope abundance from isotope masses and percentage composition, including enriched samples and molecular isotopic composition.
Compare isotope physical and chemical behaviour by relating mass or nuclear composition to density, radius, ionization energy, chemical properties and isotope peak combinations.

[Maximum number: 3]

The element boron has two naturally occurring isotopes, ${ }^{10} \mathrm{~B}$ and ${ }^{11} \mathrm{~B}$ .

(a)

Define the term isotopes of an element.

[ 1 ]

(b)

Calculate the percentage abundance of each isotope, given that the relative atomic mass of B is 10.81 .

[ 2 ]

$\quad 10 x+11(1-x)=10.81, x=0.19$ ;

Marking guidance:

Accept similar method.
${ }^{10} B: 19 \%$ and ${}^{11}\mathrm{B}: 81\%$ ;

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IB Chemistry SL 1.2.2 Isotopes Questions question 1

Question (a)

Question (b)