Explanation:
Roentgenium is a radiactive element which is represented by symbol Rg. Atomic number of Rg is 111 and its atomic mass is 272.
It is known that atomic number is the number of protons present in an atom. Whereas atomic mass is the sum of total number of protons and neutrons present in an atom.
That is, Atomic mass = no. of protons + no. of neutrons
272 = 111 + no. of neutrons
no. of neutrons = 272 - 111
= 161
Thus, we can conclude that there are 161 neutrons present in Rg-272.
