The atomic mass of gold (au) is 198, and the atomic number of gold is 79. how many neutrons does a neutral atom of gold contain?

Atomic mass is found by adding the number of protons + number of neutrons, as their atomic weights are both 1 atomic mass unit (amu). The Atomic number is the number of protons only. If gold has an atomic mass of 198, subtract the atomic number (79) to find number of neutrons: 198-79=119 neutrons