Hg₂²⁺

Note that mercury (I) is diatomic, meaning it is two Hg⁺ ions combined.  So even though it is mercury (I), the overall charge is 2+. 

H^-

Note: Hydrogen usually takes a 1+ charge.  However, when it bonds to a metal, it become a hydride and takes a 1- charge. 

fluoride

Note: Many students spell fluoride incorrectly. Take note that it is not flOUride--> DON'T write flour, as in the white powder you bake with. 

NH₄⁺

Note: While the ammonium ion is composed of only non-metals, it bonds IONICALLY.  It is an exception to the rule that ionic bonding occurs only between metals and nonmetals. 

C₂H₃O₂^-

Note: Acetate can also be written as CH₃COO^-

hydrogen

carbonate

hydrogen

sulfate

hydrogen

phosphate

hydrofluoric acid

Note: Many students spell hydrofluoric incorrectly.  Remeber "flUOric" is NOT "flOUric" 

HC₂H₃O₂

NOTE:  Acetic acid can also be written as HCH₃COO or CH₃COOH.