How many electrons can the first shell of an atom contain?

• A. 2
• B. 8
• C. 18
• D. 32

Answer: (A)

The first shell of an atom, also known as the K shell, can contain a maximum of two electrons. This limitation is based on the principles of quantum mechanics and the structure of atomic orbitals. The first shell consists of one orbital type (the s orbital), which can hold a maximum of two electrons. This is a fundamental concept in atomic theory and is crucial when understanding how electrons are arranged in an atom.

As atoms increase in size and additional shells are added, the capacity for electron storage in subsequent shells increases; for instance, the second shell can hold up to eight electrons. However, focusing solely on the first shell emphasizes its specific limitation of two electrons, which is vital for the formation of chemical bonds and the overall stability of the atom.