Question

The sum of protons, electrons and neutrons in the heaviest isotope of hydrogen is:

• A. $6$
• B. $5$
• C. $4$
• D. $3$

Answer 1

The correct option is C $4$

The heaviest isotope of hydrogen is tritium ${}_1{T}^3$ with atomic number $1$ and mass number $3$. It contains $1$ electron, $1$ proton and $2$ neutrons. The sum is $1+1+2=4$.