When an atom loses one or more electrons, it forms a/ an
Cation
The explanation for the correct option:
(B)
Cation: Loss of electrons from atom results in the formation of an ion known as a cation. For example; the cation of Sodium().
The explanation for the incorrect option:
(A)
Anion: The gain of electrons from atom results in the formation of an ion known as an anion. For example; the anion of Chlorine().
(C)
Compound: Compounds are chemical substances made up of two or more elements that are chemically bound together in a fixed ratio.
For example, Hydrochloric () is a combination of Hydrogen() and Chlorine()
(D)
Molecule: A molecule is defined as the smallest unit of a compound that contains the chemical properties of the compound.
For example; Water (), Table salt() etc,
Hence, the correct option is B.