Which term describes a positively charged atom?

The term that accurately describes a positively charged atom is "Ion." An ion is formed when an atom gains or loses one or more electrons, resulting in an electrical charge. Specifically, when an atom loses electrons, it has more protons than electrons, leading to a positive charge. This process is a key concept in chemistry and physics, as it affects how atoms interact with one another, especially in chemical reactions and electrical conductivity.

The other choices relate to general classifications of matter rather than specifically describing a charged atom. An atom refers to the basic unit of matter, a molecule is a group of two or more atoms bonded together, and an isotope pertains to atoms of the same element that have different numbers of neutrons, which affects their mass but not their overall charge. Therefore, Ion is the most precise term for a positively charged atom.