In what state is equilibrium achieved in atoms?

Equilibrium in atoms is achieved when protons equal electrons. This balance is crucial for the stability of an atom because protons carry a positive charge and electrons carry a negative charge. When the number of protons and electrons is the same, their charges cancel each other out, resulting in a neutral atom. This state of neutrality is important as it enables the atom to be stable and interact appropriately with other atoms.

When protons and electrons are unequal, the atom becomes either positively charged (if there are more protons than electrons) or negatively charged (if there are more electrons than protons), which impacts its chemical behavior and interactions with other atoms. The other choices refer to conditions that either disrupt this balance or involve scenarios that do not affect atomic equilibrium directly. Thus, the equal number of protons and electrons is the defining state for an atom's equilibrium.