IONS AND IONIC COMPOUNDS – IMPORTANT TERMS
YOU MUST KNOW THESE!
IONS
ION -- ATOM OR GROUP OF ATOMS WITH A CHARGE (this means that there are unequal numbers of
protons and electrons). CATIONS are positive (less electrons than protons), and ANIONS are negative
(more electrons than protons).
MONATOMIC ION – An ion made up of only 1 atom
EXAMPLES: ClFe+3 S-2
Li+1
POLYATOMIC ION -- An ion made up of 2 or more atoms. (Note: When writing the formula for an
ionic compound which contains a polyatomic ion, you must place the polyatomic ion in parentheses
in order to indicate how many are necessary for the compound formula)
EXAMPLES: SO3-2
NH4+1
CN-1
PO4-3
IONIC COMPOUNDS
IONIC COMPOUND – compound which forms due to electron transfer and the subsequent attraction of a
cation for an anion.
BINARY IONIC COMPOUND – ionic compound composed of only 2 different atoms. Please note
that these compounds always contain two different _______________________ _________
EXAMPLES:
NaCl CaO MgF2
Al2S3 Sn3N4
TERNARY IONIC COMPOUND – ionic compound composed of 3 or more different atoms. Please
note that these ionic compounds always contain a _______________________ _________.
EXAMPLES: FeSO3 Cr2(C2O4)3
Ba(OH)2
(NH4)3PO4