Usage - Pronoun-Antecedent Agreement. A pronoun is a word used to stand for (or take the place of) a noun. A word can refer to an earlier noun or pronoun in the sentence. Example:
A subatomic particle is a unit of matter or energy that's the fundamental makeup of all matter. According to modern atomic theory, an atom has a nucleus, which is its center, or core. The nucleus contains subatomic particles: protons and neutrons. Protons are positively-charged particles. Neutrons are neutral particles.
A proton is a positively charged particle located in the nucleus of an atom. An electron has $\frac{1}{1836}$ times the mass of a proton, but an equal and opposite negative charge. An elementary charge -- that of a proton or electron -- is approximately equal to 1.6Ã10-19Coulombs. Unlike protons, electrons can move from atom to atom. If an atom has an equal number of protons and electrons, its net charge is 0. If it gains an extra electron, it becomes negatively charged and is known as an anion.