IB Chemistry SL 1.2 The Nuclear Atom

Practise deducing particle counts from nuclear symbols, distinguishing isotopes and calculating relative atomic mass from isotope masses and abundances.

Exam points

deduce proton, neutron and electron counts from nuclear notation and ionic charge
calculate relative atomic mass as a weighted mean of isotope masses and abundances

Covered syllabus points

1.2.1—Atomic structure 1.2.2—Isotopes

[Maximum number: 1]

Titanium is a transition metal.

State the number of protons, neutrons and electrons in the ${ }_{22}^{48} \mathrm{Ti}$ atom.

Protons:

Neutrons:

Electrons:

[Maximum number: 4]

Chlorine occurs in Group 7, the halogens.

(a)

Two stable isotopes of chlorine are ${ }^{35} \mathrm{Cl}$ and ${ }^{37} \mathrm{Cl}$ with mass numbers 35 and 37 respectively.

[ 4 ]

(i)

Define the term isotopes of an element.

[ 2 ]

(ii)

Using the mass numbers of the two isotopes and the relative atomic mass of chlorine from Table 5 of the Data Booklet, determine the percentage abundance of each isotope.

Percentage abundance ${ }^{35} \mathrm{Cl}$ :

Percentage abundance ${ }^{37} \mathrm{Cl}$ :

[ 2 ]

$\left(\right.$ for $\left.{ }^{35} \mathrm{Cl}: x \%\right) 35 x+3700-37 x=3545$ ;

Marking guidance:

Allow other alternative mathematical arrangements.
${ }^{35} \mathrm{Cl}=77.5 \%$ and ${ }^{37} \mathrm{Cl}=22.5 \%$ ;

Award [1 max] for correct percentages if no correct working is shown.

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Covered syllabus points

1.2 The nuclear atom question 1

1.2 The nuclear atom question 2

Question (a)

Question (i)

Question (ii)