# Ions --- **Ions** are [[charge|charged]] versions of [[atom|atoms]] or [[molecule|molecules]]. *Positively* charged ions are called **cations** and *negatively* charged ions are called **anions**. [[polyatomic ion|Polyatomic ions]] are ions that are made up of more than one atom, but still have a single overall charge. Some biologically important ions are used as [[electrolytes]], such as [[sodium]], [[potassium]], [[chloride]] and [[phosphate]]. ## Forming Ions Ions are formed usually when one, two or three electrons from an [[element]] on the left side of the periodic table (with few electrons in their [[electron shell#Valance Shell The Octect Rule|valance shell]]) move to an atom from the right side of the table which is only a one, two or three electrons shy of a full [[electron shell#Valance Shell The Octect Rule|valance shell]]. These now oppositely [[charge|charged]] ions often immediately attract and form [[ionic bond|ionic bonds]]. Some ions only have one possible charge. For example, fluoride will only every really gain one [[atom|electron]], so you only ever see F$^-$. Other ions can gain or lose two or three electrons, depending on the situation (i.e. what other atom it's reacting with). For example iron can be in Fe$^{2+}$ or Fe$^{3+}$ forms. ![[periodic table of ions.png]] ## Naming Ions Ions have special names that distinguish them from their non-ionic versions. There is a different convention for ions that have one possible charge or that have multiple possible charges. Ions that only have one charge are named differently if they are cations or anions. Cations are simply the "*name of element*" and then "ion", so for example, [[sodium|Na+]] is "sodium ion". Anions use the root of the element name and the suffix *-ide*, then "ion". For example, [[chloride|Cl-]] is "chloride". Ions with multiple possible charges use one of two suffixes, *-ic* and *-ous*. The smaller version uses the *-ous* suffix and the larger uses the *-ic* suffix. For example, iron can form Fe$^{2+}$ or Fe$^{3+}$, so these would be *ferrous* and *ferric* respectively. When writing you can also write the charge in roman numerals in parentheses after the element name, so for example iron(II) and iron(III). You never write roman numerals for ions that do not form more than one type of ion. ___