Name these compounds: (a) \(\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2} ;\) (b) \(\mathrm{HNO}_{2}\); (c) \(\operatorname{Cr} \mathrm{O}_{2} ;\) (d) \(\mathrm{KIO}_{3} ;\) (e) \(\mathrm{LiCN} ;\) (f) \(\mathrm{KIO} ;\) (g) \(\mathrm{Fe}(\mathrm{OH})_{2}\) (h) \(\mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2} ;\) (i) \(\mathrm{H}_{3} \mathrm{PO}_{4} ;\) (j) \(\mathrm{NaHSO}_{4} ;\) (k) \(\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\); (l) \(\mathrm{NH}_{4} \mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2} ;(\mathrm{m}) \mathrm{MgC}_{2} \mathrm{O}_{4} ;\) (n) \(\mathrm{Na}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\)

The first step is to know, how to name monoatomic ions. For metals in groups 1 and 2, and for metals that form cations with a single charge, the name of the metal is followed by 'ion'. For metals that form cations with more than one charge, the charge is indicated by a Roman numeral in parentheses after the name of the metal. For nonmetals, the end of the name of the element is dropped and replaced with 'ide', followed by the word 'ion'.

Polyatomic ions are composed of more than one atom. Most of them are anions, and their names end in 'ite' or 'ate'. The 'ite' ending indicates a lower oxidation number, while 'ate' indicates a higher one. The number of oxygen atoms can also influence the name: one fewer oxygen atom than the 'ite' form is indicated by the prefix 'hypo-', while one more is indicated by the prefix 'per-'.

Now, let’s name given compounds using these rules: (a) \(\mathrm{Ba(NO_{3})_{2}}\) is Barium nitrate. (b) \(\mathrm{HNO_{2}}\) is Nitrous acid. (c) \(\mathrm{CrO_{2}}\) is Chromium(IV) oxide. (d) \(\mathrm{KIO_{3}}\) is Potassium iodate. (e) \(\mathrm{LiCN}\) is Lithium cyanide. (f) \(\mathrm{KIO}\) is Potassium hypoiodite. (g) \(\mathrm{Fe(OH)_{2}}\) is Iron(II) hydroxide. (h) \(\mathrm{Ca(H_{2}PO_{4})_{2}}\) is Calcium dihydrogen phosphate. (i) \(\mathrm{H_{3}PO_{4}}\) is Phosphoric acid. (j) \(\mathrm{NaHSO_{4}}\) is Sodium hydrogen sulfate. (k) \(\mathrm{Na_{2}Cr_{2}O_{7}}\) is Sodium dichromate. (l) \(\mathrm{NH_{4}C_{2}H_{3}O_{2}}\) is Ammonium acetate. (m) \(\mathrm{MgC_{2}O_{4}}\) is Magnesium oxalate. (n) \(\mathrm{Na_{2}C_{2}O_{4}\) is Sodium oxalate.