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.
Any atom or group of atoms with a net charge (whether positive or negative) is called an ion. A positively charged ion is a cation while a negatively charged ion is an anion. Now we are ready to discuss the periodic trends of atomic size, ionization energy, electron affinity, and electronnegativity.