Chemical Nomenclature
Name and write formulas for ionic compounds, covalent compounds, acids, and hydrates using standard naming rules.
A lesson of Chemistry, in Chemical Bonding and Molecular Structure, about 35 minutes.
By the end of this lesson, you will be able to decide which naming system a compound uses, name ionic and covalent compounds and acids, and go backwards from a name to a formula.
Decide the Type First
Naming is three separate systems, and the only real skill is choosing between them before you start. Look at the first element.
$$\textbf{metal + nonmetal} \Rightarrow \text{ionic}$$
$$\textbf{nonmetal + nonmetal} \Rightarrow \text{covalent}$$
$$\textbf{starts with H, dissolved in water} \Rightarrow \text{acid}$$
Get this wrong and everything after it is wrong, because the systems disagree about the most visible thing: prefixes.
$$\mathrm{CO} = \text{carbon monoxide} \qquad \text{covalent, prefixes used}$$
$$\mathrm{CaO} = \text{calcium oxide} \qquad \text{ionic, no prefixes}$$
Two oxides, two rules, and the difference is whether the first element is a metal.
Why the systems differ. In an ionic compound the charges fix the ratio, so there is nothing to disambiguate: calcium is always $+2$ and oxygen always $-2$, so calcium oxide can only be $\mathrm{CaO}$. Nonmetals share rather than transfer, and the same two elements can combine in several ratios, so the count has to be stated. $\mathrm{CO}$ and $\mathrm{CO_2}$ are both real, and one of them is lethal.
Sort It: Which Naming System
Ionic: No Prefixes, Sometimes a Numeral
Metal name unchanged, then the nonmetal ending in -ide.
$$\mathrm{NaCl} = \text{sodium chloride} \qquad \mathrm{Al_2O_3} = \text{aluminum oxide}$$
Never a prefix. Aluminum oxide, not "dialuminium trioxide". The subscripts are forced by the charges, so stating them adds nothing.
A Roman numeral for metals with more than one charge, which means the transition metals plus lead and tin:
$$\mathrm{FeO} = \text{iron(II) oxide} \qquad \mathrm{Fe_2O_3} = \text{iron(III) oxide}$$
The numeral is the metal's charge, found by balancing against the anions.
No numeral needed for group 1 and 2 metals, aluminum, zinc or silver, which have only one charge each.
Polyatomic ions keep their names:
$$\mathrm{Ca(NO_3)_2} = \text{calcium nitrate} \qquad \mathrm{NaOH} = \text{sodium hydroxide}$$
And the -ate/-ite pair is about oxygen count, not charge: sulfate is $\mathrm{SO_4^{2-}}$ and sulfite is $\mathrm{SO_3^{2-}}$, same charge and one fewer oxygen. -ate has more oxygen, and that single rule covers nitrate and nitrite, phosphate and phosphite, chlorate and chlorite.
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