An isotope with mass number 81 has eleven more neutrons than protons.This is an isotope of what element?
A)Tl
B)Yb
C)Zr
D)Br
E)Nb

Question

Quizplus · Accepted Answer

The mass number is the sum of protons and neutrons. If the isotope has 11 more neutrons than protons, let the number of protons be P. Then, the number of neutrons is P + 11. The mass number is P + (P + 11) = 81, which simplifies to 2P + 11 = 81. Solving for P gives P = 35, which corresponds to the element Bromine (Br).

An Isotope with Mass Number 81 Has Eleven More Neutrons