The first energy level of an atom can hold how many electrons?

The first energy level of an atom, which is also known as the K shell or principal quantum level n=1, can accommodate a maximum of 2 electrons. This limitation arises due to the principles of quantum mechanics, specifically the Pauli Exclusion Principle, which states that no two electrons can have the same set of quantum numbers. Since the first energy level has only one s orbital, it can hold a maximum of 2 electrons with opposite spins.

In contrast, higher energy levels can hold more electrons, such as the second energy level, which can hold up to 8 electrons, and the third energy level, which can hold up to 18 electrons. Therefore, understanding the electron configuration and the specific capacities of each energy level is vital in comprehending atomic structure and behavior.