An element with mass number 81 contains 31.7% more neutrons as compared to protons. Assign the atomic symbol.

Given:

Mass Number = 81

Percentage of neutron = 31.7% more as compared protons

Let number of protons = p

Let number of neutrons= n

p + n = 81

p + {p + [31.7× p] / 100} = 81

p + 1.317p = 81

2.317p = 81

p = 81 / 2.317

p = 94.95899

p = 35

Atomic Number = 35

The element is bromine.

The atomic symbol is 81₃₅Br.