ION

An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. An anion (pronounced /ˈæn.aɪ.ən/ AN-eye-ən), from the Greek word ἀνω (anο), meaning "up", is an ion with more electrons than protons, giving it a net negative charge (since electrons are negatively charged and protons are positively charged). Conversely, a cation (pronounced /ˈkæt.aɪ.ən/ KAT-eye-ən), from the Greek word κατά (kata), meaning "down", is an ion with more protons than electrons, giving it a positive charge.

An ion consisting of a single atom is a monatomic ion. If it consists of two or more atoms, it is a polyatomic ion. Polyatomic ions containing oxygen, such as carbonate and sulfate, are called oxyanions. When writing the chemical formula for an ion, its charge is written as a superscript "+" or "−" (depending on if the ion is positive + or negative −) following a number indicating the difference between the number of protons and the number of electrons. The number is omitted if it is equal to 1. For example, the sodium cation is written as Na+, the "+" indicating that it has one fewer electron than it has protons. The sulfate anion is written as SO2−4, the "2−" indicating that it has two more electrons than it has protons. If an ion contains unpaired electrons, it is called a radical ion. Just like neutral radicals, radical ions are very reactive.
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Ion adalah atom atau sekumpulan atom yang bermuatan listrik. Ion bermuatan negatif, yang menangkap satu atau lebih elektron, disebut anion, karena dia tertarik menuju anoda. Ion bermuatan positif, yang kehilangan satu atau lebih elektron, disebut kation, karena tertarik ke katoda. Proses pembentukan ion disebut ionisasi. Atom atau kelompok atom yang terionisasi ditandai dengan tikatas n+ atau n-, di mana n adalah jumlah elektron yang hilang atau diperoleh.