What is the term for the lowest energy level on an energy graph?

The term for the lowest energy level on an energy graph is referred to as the ground term. In quantum mechanics and atomic theory, the ground state represents the lowest possible energy state of a system, such as an atom or molecule. This is where the electrons are in their lowest energy configuration, allowing for a stable arrangement without any excitation.

When an atom is in its ground state, all of its electrons are in the lowest energy orbitals available to them. This state is crucial for understanding various phenomena in chemistry, including reactivity, spectroscopic properties, and the stability of the atom or molecule.

In contrast, excited terms refer to any state where electrons have absorbed energy and moved to higher energy levels, which are not considered the most stable configuration. The singlet and triplet states specifically describe the spin configurations of electron pairs in the excited state, further emphasizing that they are not at the minimum energy level. Thus, the ground term correctly identifies the foundational state from which all electron excitations and transitions begin.