How many shells are occupied by electrons in the gold atom (au, atomic# 79) (hint: refer to the shell model of the atom)?

Gold has an atomic number 79.
This means that the number of protons in gold is 79.
Since the number of electrons is equal to the number of protons, this means that gold has 79 electrons.

The electronic configuration of gold can be illustrated as follows:
[Xe] 4f14  5d10  6s1

From the above configuration, we can deduce that:
6 shells are occupied by electrons in gold

They can measure  the amount of energy gained or lost