When an atom is missing an electron, it is __________.

When an atom is missing an electron, it becomes ionized. This process occurs because atoms are generally neutral, with an equal number of protons and electrons. The removal of an electron results in a net positive charge due to the imbalance between the positively charged protons and the negatively charged electrons. This charged particle is known as a cation.

Ionization is a significant concept in chemistry and physics as it plays a crucial role in the behavior of atoms and their ability to form chemical bonds. When atoms ionize, they can interact differently with other atoms or molecules, impacting various chemical reactions and processes.

The other options do not accurately describe the state of an atom missing an electron; for example, if the atom were stabilized or aggregated, it would likely not have lost an electron. Thus, ionization clearly describes the condition of an atom that has lost an electron.