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Q.
Hydrogen has three isotopes (A), (B) and (C). If the number of neutron(s) in (A), (B) and (C) respectively, are (x), (y) and (z), the sum of (x), (y) and (z) is :
Hydrogen has three isotopes
$\begin{matrix}Isotopes&Number\, of \,neutrons\\ Protium\,\left(^{1}_{1}H\right)&0\\ Deutrium\,\left(^{2}_{1}H\right)&1\\ Tritium\,\left(^{3}_{1}H\right)&2\\ &\end{matrix}$
Hence the sum of neutrons are 3