Chemistry Practice Test: Naming Compounds

The prefix di- means two nitrogen atoms and tri- means three oxygen atoms, so the formula is N₂O₃. N₃O₂ swaps the two numbers.

Chloride is 1−, so copper must be +1 here, which the Roman numeral (I) shows. Copper(II) chloride is CuCl₂, and prefixes like mono- are not used in ionic names.

Sulfate is SO₄²⁻, so two Na⁺ ions are needed. Na₂SO₃ is sodium sulfite and Na₂S is sodium sulfide.

ClO₃⁻ is the chlorate ion. Chlorite has one fewer oxygen (ClO₂⁻), perchlorate has one more (ClO₄⁻), and chloride is just Cl⁻.

Three Ca²⁺ ions (+6) balance two PO₄³⁻ ions (−6). The parentheses show that the whole phosphate ion is taken twice.

NH₄⁺ is the ammonium ion and NO₂⁻ is nitrite. Ammonium nitrate would be NH₄NO₃, with one more oxygen.

H₂SO₃ contains the sulfite ion, and an -ite ion gives an -ous acid. Sulfuric acid is H₂SO₄ (from sulfate), and hydrosulfuric acid is H₂S, which has no oxygen.

The prefix hydro- marks an acid with no oxygen, made of hydrogen and a single nonmetal. Fluoride is F⁻, so one hydrogen is enough: HF dissolved in water.

Transition metals like iron can form Fe²⁺ or Fe³⁺, so the numeral tells which ion is present. It gives the charge of the metal ion, not the number of chloride ions, even though both happen to be 3 here.

SF₆ is made of two nonmetals, so prefixes are used: hexa- for six fluorine atoms. The first element gets no prefix when there is only one atom of it.