## Chemistry: Molecular Approach (4th Edition)

$\underline{\text{H-2}}$
The number of neutrons of hydrogen is 1.The atomic number of hydrogen is 1 from the periodic table. The number of protons is given by the atomic number. So, the number of protons is 1. The relation between the mass number, the number of protons, and the number of neutrons is as follows: $A=\text{Number of protons}+\text{Number of neutrons}$ Here, A is the mass number. Calculate the mass number as follows: \begin{align} & A=1+1 \\ & =2 \end{align} The notation for the isotope is as follows: $\text{X-}A$ Here, A is the mass number and X is the chemical symbol. So, the isotopic symbol for the hydrogen isotope with 1 neutron is $\underline{\text{H-2}}$.