Explain why a hydrogen atom can become either an ion or a part of a molecule
Hydrogen is an element with atomic number 1. It has only one electron in its electron configuration that is `1s^1` . The closest stable electron configuration for an atom with one electron is `1s^2` that is the electron configuration of the noble gas helium.
When a hydrogen atom loses an electron its electron configuration is `1s^0` . A hydrogen ion `H^+` cannot exist as such due to the positive charge it carries. It immediately combines with any negatively charged particles around it to form ionic bonds.
Hydrogen also forms covalent bonds where a stable electron configuration of `1s^2` is achieved by the atom sharing an electron with another atom. For example, two hydrogen atoms combine to form the gas `H_2` where the electrons of each of the constituent atoms provide one electron so that the each atom has a stable electron configuration.