Question

Name each ionic compound. $$ \text { a. }\mathrm{SnCl}_{4} \quad \text { b. } \mathrm{PbI}_{2} \quad \text { c. } \mathrm{Fe}_{2} \mathrm{O}_{3} $$ $$ \mathrm{d.} \mathrm{Cul}_{2} \quad \text { e. } \mathrm{HgBr}_{2} \quad \text { f. } \mathrm{CrCl}_{2} $$

Short answer

a. Tin(IV) chloride, b. Lead(II) iodide, c. Iron(III) oxide, d. Copper(I) iodide, e. Mercury(II) bromide, f. Chromium(II) chloride

Step-by-step solution

Recognize the Metal in Each Compound

Identify the metal in each compound and check whether it is an element with a fixed charge or one that can have multiple charges.

Determine the Ionic Charges

For metals with a fixed charge, assign their known charge. For metals that can have multiple charges, use the anion to determine the metal's charge.

Name the Compounds with Fixed Charge Metals

If the metal has a fixed charge, simply name the metal followed by the name of the non-metal with its ending changed to 'ide'.

Name the Compounds with Variable Charge Metals

If the metal can have multiple charges, write the name of the metal followed by the charge in roman numerals in parentheses, and then the non-metal with 'ide' as the ending.

Key concepts

Chemical Nomenclature

Understanding chemical nomenclature is essential for identifying and communicating about compounds in chemistry. It's like knowing the proper names of people in order to address them correctly. In ionic compounds, the name typically consists of the cation (positive ion) followed by the anion (negative ion). When we follow this rule, tin(IV) chloride becomes the name for \texttt{SnCl\(_4\)}, since tin can have multiple oxidation states and the chloride ion carries a -1 charge. Lead(II) iodide is named for \texttt{PbI\(_2\)}, with lead carrying a +2 charge as indicated by the (II). For compounds with metals having fixed charges, such as sodium chloride (\texttt{NaCl}), there's no need for charge indication as sodium always has a +1 charge.

When naming compounds with polyatomic ions, the ion's formal name is used, such as sulfate for \texttt{SO\(_4^{2-}\)} or nitrate for \texttt{NO\(_3^{-}\)}. But if you're faced with something like iron(III) oxide (\texttt{Fe\(_2\)O\(_3\)}), you need to indicate the iron's oxidation state because it can vary.

Oxidation States

In chemical compounds, atoms can 'lose' or 'gain' electrons, resulting in a charge; this charge is known as the oxidation state. In ionic compounds, the total charge must balance out to zero. That means for \texttt{Fe\(_2\)O\(_3\)}, with oxygen usually carrying a charge of -2, iron must have a charge of +3 to neutralize the three doubly-charged oxygen ions. This is how we deduce that iron has an oxidation state of III, leading to the name iron(III) oxide.

Oxidation states are usually straightforward for metals in groups 1 and 2 of the periodic table since they have fixed charges (+1 and +2, respectively). However, transition metals can have several possible oxidation states. This is why we see names like manganese(II) oxide or lead(IV) acetate, where the Roman numeral indicates the metal's charge.

Polyatomic Ions

Many ionic compounds include polyatomic ions, which are charged entities composed of two or more atoms bonded together. For instance, \texttt{NH\(_4^+\)} is the ammonium ion, a cation, and \texttt{PO\(_4^{3-}\)} is the phosphate ion, an anion. When naming ionic compounds involving these ions, we use the polyatomic ion's name as part of the compounds name. For example, ammonium chloride (\texttt{NH\(_4\)Cl}) or calcium sulfate (\texttt{CaSO\(_4\)}).

Recognizing common polyatomic ions is a key part of mastering chemical nomenclature. They often end in '-ate' or '-ite', indicating different numbers of oxygen atoms (e.g., nitrate is \texttt{NO\(_3^{-}\)} and nitrite is \texttt{NO\(_2^{-}\)}). Understanding and memorizing the names and formulas of common polyatomic ions will dramatically simplify the task of naming ionic compounds.