Question

There are five naturally occurring isotopes of zinc:${}_{30}{}^{64}Zn$,${}_{30}{}^{66}Zn$,${}_{30}{}^{67}Zn$,${}_{30}{}^{68}Zn$, and ${}_{30}{}^{70}Zn$ . None of these isotopes has the atomic mass of $65.41$ listed for zinc on the periodic table.
Explain.

Short answer

These five isotopes has different number of neutron.

Step-by-step solution

Given information.

We have been given that,

${}_{30}{}^{64}Zn,{}_{30}{}^{66}Zn,{}_{30}{}^{67}Zn,{}_{30}{}^{68}Zn,{}_{30}{}^{70}Zn$

We need to explain why no isotopes atomic mass equals to that of given atomic mass of zinc.

Explanation.

Firstly, Atomic mass depends on the sum of number of neutron and protons.

Since, these five isotopes has different number of neutron ,therefore there atomic mass is different from each other and to that of atomic mass of zinc.

Also, atomic mass of zinc is the average atomic mass of five isotopes.