What is the maximum capacity of electrons in the third shell of an atom?

The maximum capacity of electrons in the third shell of an atom is indeed 18. To understand this, one must consider the rules governing electron configuration in atomic structure.

The electron shells are organized according to the principal quantum number, which indicates their relative energy levels and distance from the nucleus. The formula for determining the maximum number of electrons that any given shell can hold is 2n², where n is the principal quantum number of the shell.

For the third shell, where n equals 3, the calculation is as follows:

2n² = 2(3)² = 2(9) = 18 electrons.

This means the third shell can accommodate up to 18 electrons due to its energy level and the availability of subshells (s, p, d) within that shell. Each subshell can hold a specific number of electrons (2 for s, 6 for p, and 10 for d), and cumulatively, these add up to 18 when all are considered in the third shell context.