An element with mass number 81 contains 31.7% more neutrons as compared to protons. Find the symbol of the atom.

Explanation

Mass number of the given element = 81
Suppose the element contains p protons.
Number of neutrons (n) `=p +(p xx 31.7)/(100)`
=1.317 p
p+n=81
p+1.317 p=81
`p=(81)/(2.317) =34.96 =35`
Thus, atomic number of the element = p = 35, i.e., the element is bromine.
Hence, the symbol is `""_(35)^(81)" Br."`