What is an atomic orbital?

• A. A region of space around the nucleus that can be occupied by up to two electrons
• B. A probability cloud for a pair of electrons
• C. A fixed distance from the nucleus
• D. A type of chemical bond

Answer: (A)

An atomic orbital is a region around the nucleus where there is a high probability of finding an electron. It’s defined by quantum numbers and has a specific shape and energy. Importantly, an orbital can hold up to two electrons, as long as their spins are opposite, reflecting the Pauli exclusion principle. Electrons don’t follow fixed paths at precise distances from the nucleus; instead, their positions are described by a probability distribution or “cloud.” The other ideas—being a fixed distance or a type of chemical bond—don’t fit this quantum description.