Question

Determine the total number of neutrons in three isotopes of hydrogen.

Answer 1

Isotopes are species that posses same number of protons and electrons but different number of neutrons.
Three isotopes of Hydrogen were
${}_1{H}^1$, ${}_1{D}^2$, ${}_1{T}^3$
$\text{Number of neutron = Mass number}-\text{Number of proton}$
${}_1{H}^1$ : Number of neutron = 1 $-$ 1 = 0
${}_1{D}^2$ : Number of neutron = 2 $-$ 1 = 1
${}_1{T}^3$ : Number of neutron = 3 $-$ 1 = 2
Total number of neutrons = 0 + 1 + 2 = 3
Hence, the total number of neutrons in three isotopes of hydrogen is 3.