A Level Chemistry OCR Practice Exam

The term that describes a collection of atomic orbitals of the same type within a shell is known as a sub-shell. In the context of atomic structure, each principal energy level, or shell, can contain one or more sub-shells, which are designated as s, p, d, and f. Each type of sub-shell is characterized by distinct shapes and arrangements of orbitals: for instance, an s sub-shell has one spherical orbital, a p sub-shell has three dumbbell-shaped orbitals, and so forth. This concept is fundamental to understanding the organization of electrons in atoms and how they influence chemical bonding and properties.

The other terms mentioned refer to different concepts: a substitution reaction relates to a type of chemical reaction where one functional group in a molecule is replaced by another, molecular arrangement pertains to how atoms are arranged within a molecule, and hybrid orbitals refer to a concept where atomic orbitals combine to form new orbitals that are suitable for pairing electrons to form chemical bonds. Each of these does not specifically denote a collection of orbitals of the same type within a shell, making sub-shell the most accurate choice for this question.