# Zirconium has an atomic number of 40 and an atomic mass of 91. How many neutrons does it have?

Jun 14, 2016

51 neutrons

#### Explanation:

The atomic mass of an element can be determined by adding the protons and the neutrons.

$P + N = A M$

$N = A M - P$

$N = {91}^{a m} - {40}^{+}$

$N = 51$