The neutron number plays a key role in distinguishing different classes of nuclides.

CHEMISTRY · Multi-part · A Level · Chemistry · Atomic structure · Atomic structure

Problem

The neutron number plays a key role in distinguishing different classes of nuclides. (i) Explain why two nuclides having the same mass number

A

but different atomic numbers

Z

cannot be isotopes of each other. (ii) The nuclides

^{40}_{18}\!\text{Ar}

^{40}_{20}\!\text{Ca}

and

^{42}_{20}\!\text{Ca}

are provided. Compare each pair and state clearly whether they are isotopes, isobars or isotones. Justify your answer on the basis of

Z

A

and

N

. (iii) Give one reason why isotopes of an element exhibit nearly identical chemical behaviour whereas isobars do not necessarily do so.