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Monatomic cations are named using the name of the element followed by a Roman numeral if the element can have more than one charge. For elements with a fixed charge, only the element name is used.- (a) \( \mathrm{Ba}^{2+} \): Barium has a fixed +2 charge, so it is called **barium ion**.- (b) \( \mathrm{Cs}^{+} \): Cesium has a fixed +1 charge, so it is called **cesium ion**.- (c) \( \mathrm{V}^{3+} \): Vanadium can have multiple charges; thus it is named using a Roman numeral as **vanadium(III) ion**.- (f) \( \mathrm{Ni}^{2+} \): Nickel can have multiple charges; thus it is named using a Roman numeral as **nickel(II) ion**.- (i) \( \mathrm{Mn}^{2+} \): Manganese can have multiple charges; thus it is named using a Roman numeral as **manganese(II) ion**.

Polyatomic ions and single-element anions have specific names often ending in -ide, -ate, or -ite. - (d) \( \mathrm{HCO}_{3}^{-} \): Known as the **bicarbonate ion** or **hydrogen carbonate ion**.- (e) \( \mathrm{NH}_{4}^{+} \): Known as the **ammonium ion**.- (g) \( \mathrm{NO}_{2}^{-} \): Known as the **nitrite ion**.- (h) \( \mathrm{ClO}_{2}^{-} \): Known as the **chlorite ion**.- (j) \( \mathrm{ClO}_{4}^{-} \): Known as the **perchlorate ion**.