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

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