Ionic Bond Formation

1. Subtract the electronegativity values. An ionic bond should have a value GREATER THAN Is the compound made from a metal and a non-metal?

Rules for Writing Ionic Compounds 1.Determine the Oxidation Numbers of the elements combined. Recall that the oxidation number is the number of electrons an atom gains or loses when it forms chemical bonds.

For Alkali and Alkaline Earth Metals the oxidation number is the same as the valence. Family #1 loses the valence electron to form a +1 charge, its oxidation # is +1 Family #2 loses 2 valence electrons to form a +2 charge, its oxidation # is +2

For NON Metals, the oxidation number is the number of electrons ADDED to make a total of 8 valence electrons. Ex: Halogens have 7 valence and need only 1 to complete total to 8, therefore their oxidation number is - 1 Oxygen Family have 6 valence e - and need only 2 to complete 8, therefore their oxidation number is - 2

Monatomic ions Monatomic cations- a one atom positive ion Ex: Na + Mg +2 Al +3 Monatomic anions- one atom negative ion EX: F - 1 O - 2 N - 3

2.Always write the element with the + oxidation number first. 3.Criss -Cross the oxidation number (without signs) so they now become subscripts. Subscripts are lower numbers that tell the number of atoms of that compound.

4.If the subscripts have greatest common factors reduce them. EXCEPT: Hg 2 Cl 2 and H 2 O 2 5. When elements combine they are stable and electrically neutral

Br -1 S -2 N -3 F -1 Ag + K+K+ Mg +2

TERMS TO REMEMBER CATION – The positive ion formed when an atom LOSES an electron. ANION- The negative ion formed when an atom GAINS an electron.

NAMING IONIC COMPOUNDS Write the name of the cation first—DO NOT AMEND THE NAME Change the name of the anion ending to ---IDE EX: sodium chloride, sodium oxide, calcium bromide, magnesium sulfide aluminum nitride, iron fluoride

Now lets name these: Br -1 S -2 N -3 F -1 Ag + K+K+ Mg +2