Final answer:
In Chemistry, shells are the main energy levels in an atom, while subshells group orbitals of similar energy and orbitals are regions within subshells where electrons are likely found. Shapes and orientations of orbitals are defined by quantum numbers. Molecular orbitals arise from atomic orbital combinations and are categorized as bonding or antibonding.
Step-by-step explanation:
The question posed by the student deals with the concept of molecular orbitals, quantum chemistry, and orbital shapes and orientations, which are fundamental topics within the field of Chemistry. Shells, subshells, and orbitals are concepts in atomic structure that explain the behavior and properties of electrons within an atom.
Shells are the main energy levels that can hold electrons and are organized based on increasing energy. Subshells are divisions within shells that group orbitals of similar energy together. Orbitals are the specific regions within subshells where there is a high probability of finding an electron, and each orbital can hold a maximum of two electrons with opposite spins.
The exact shape and orientation of these orbitals are determined by quantum numbers, which were not used in the description to answer the question.
In molecular orbital theory, the atomic orbitals combine to form molecular orbitals that can either be bonding, increasing electron probability between nuclei, or antibonding, with regions of zero electron probability called nodes.