A Level Chemistry OCR Practice Exam

What defines an atomic orbital?

1. A fixed orbit of electrons

2. A region within an atom for two electrons

3. A wave function for the nucleus

4. A particle with a positive charge

The correct answer is: A region within an atom for two electrons

An atomic orbital is indeed best defined as a region within an atom where there is a high probability of finding electrons. This concept arises from quantum mechanics, where electrons are described not as fixed particles moving in set paths (which would be an orbit), but as wave functions that give rise to various shapes where they are likely to be located. In this context, a single atomic orbital can hold a maximum of two electrons with opposite spins, thus emphasizing that it's about the region where these electrons are likely to be found rather than a fixed path or specific location in the classical sense. This definition aligns with the nature of atomic orbitals, where they are often depicted as three-dimensional shapes representing the probability distribution of the electrons. The other options do not accurately capture the essence of what an atomic orbital is. A fixed orbit suggests a classic view inconsistent with quantum mechanics, while a wave function pertaining to the nucleus focuses on a different aspect of atomic structure, and a particle with a positive charge does not relate to the definition or function of an orbital itself.