BIO101: Introduction to Molecular and Cellular Biology

Atoms have a specific structure that determines their behavior in an element or compound. Electrons occupy spaces around the nucleus. These spaces have a hierarchical arrangement. An orbital is a space that can be occupied by electrons. Each orbital can contain up to two electrons.

There are different types and shapes of orbitals: s, p, d, and f. There is only one kind of s orbital, but there are three kinds of p orbital, five d orbitals, and seven f orbitals. A collection of orbitals of the same type makes up a subshell, and a collection of subshells makes up a shell (also called an energy level). The first shell includes only one subshell (the s subshell), which is made up of only one s orbital. The second shell is made up of two subshells (an s and a p subshell), with the s subshell being made up of one s orbital and the p subshell being made up of three p orbitals. Since different shells contain different numbers of orbitals, each shell has a different maximum number of electrons it can hold.

Watch this lecture to learn about orbitals and review the structure of an atom.