Relative atomic mass
3 marks · EasyThe element oxygen has three naturally occurring isotopes: ^{16}O, ^{17}O and ^{18}O.
State what is meant by the term 'isotope'.
State one thing that all isotopes of oxygen have the same.
State one way in which isotopes of oxygen differ.
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(a) Atoms of the same element with the same number of protons but different numbers of neutrons
(b) Number of protons (or atomic number / number of electrons / chemical properties)
(c) Number of neutrons (or mass number / relative atomic mass / physical properties)
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Marking points
B1 (a) · 1 mark · Correct definition of isotope (same number of protons, different number of neutrons).
B2 (b) · 1 mark · Any one correct similarity (e.g., same number of protons/atomic number).
B3 (c) · 1 mark · Any one correct difference (e.g., different number of neutrons/mass number).
Worked solution
a) Isotopes are atoms of the same element (same number of protons) with different numbers of neutrons.
b) All isotopes of oxygen have the same number of protons.
c) Isotopes of oxygen have different numbers of neutrons.