Question

An element ‘X’ has mass number = 27. If the no. of electrons is given as 13, the no. of neutrons will be ___ .

(Assume that atom is neutral)

Answer 1

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

Since an atom is neutral, no. of protons = no. of electrons, which is necessary for charge balance.

Thus, number of protons is 13, as number of electrons are 13.
So, number of neutrons will be 27 – 13 = 14