Question

A certain nucleus X has a mass number of 16 and an atomic number of 7. Find the number of neutrons. The nucleus X emits one γ-ray photon. Write the symbol of the new nucleus and express the change using a reaction.

Answer 1

Mass number = No. of protons + No. of neutrons

Atomic number = No. of protons

∴ No. of neutrons = Mass number − Atomic number 

= 16 − 7

= 9

Element X can be written as \[\ce{_7^16X}\].

After the emission of one γ-ray photon, the mass number and the atomic number will remain the same. The element X stays as X in its ground state.

\[\ce{_7^16X -> _7^16X + γ-ray}\]