2.5 notes: binary and binary ionic compounds

naming binary and binary ionic compounds

• compound: two or more elements chemically bonded together to form molecules or formula units

  • binary ionic compound: a compound consisting of one metal and one nonmetal chemically bonded to form formula units, not molecules

• two types of metals

  • monovalent metals—only one charge possible

    • alkali metals (+1 charge), alkaline earth metals (+2), aluminum (+3), zinc (+2), and silver (+1)

  • multivalent metals—multiple charges possible

    • transition metals (center of the periodic table)

naming rules

• name the metal first, and written as it appears on the periodic table

• change the ending of the nonmetal to -IDE

• if the metal is multivalent, use a roman numeral to specify the charge on the metal cation. if the metal is monovalent, the charge is not specified with a roman numeral

  • eg. NaCl = sodium chloride (sodium is monovalent)

  • eg. CuO = copper (II) oxide (copper is multivalent)

• the charges of each element must add to 0

binary ionic formulas

• the positive ion (the metal) is always written first in a formula

• the sum of the charges must equal zero—the total positive charge on the positive ion(s) must equal the total negative charge on the negative ion(s)

• use subscripts if more than one ion is needed