Consider an atom of gold in which the nucleus contains 79 protons and 118 neutrons. What is its atomic number and atomic mass number? The atomic number is 79, and the atomic mass number is 197. The atomic number is 79, and the atomic mass number is 118. The atomic number is 118, and the atomic mass number is 197. The atomic number is 118, and the atomic mass number is 79.

The atomic number is 79 and the atomic mass is 197.

Explanation:

The atomic number (symbol Z) of a chemical element is the number of protons within its nucleus.

Gold (chemical symbol Au) is a chemical element with 79 protons in its nucleus, therefore with atomic number 79.

The atomic mass is the average mass of the atoms of an element (in atomic mass unit). The atomic mass is the weighted average of all the isotopes of a a particular element. For each isotope the atomic mass is approximately the mass of both protons and neutrons since electrons make minor contributions.

The atomic mass of Gold (Au) is 196.9665 but, it can be rounded to 197.