Because cations are + and anions are – they attract each other.
This attraction forms Ionic Bonds.
Ionic bonds are very strong.
Ionic Bonds are electrically neutral.
The charges cancel each other out.
You have to have the same number of + & -
Ionic bonds form salts.
NaCl KCl CaI 2 MgF 2
Monatomic or Polyatmoic?
1 atom per ion
More than one atom per ion
NH 4 +1
SO 4 -2
Polyatomic Ions NH 4 +1 All of the atoms in the ion act like ONE atom. The nitrogen and four hydrogens are like one atom with a +1 charge. You cannot separate the atoms!
To write a formula, you combine the fewest positive ions and negative ions to make the total charge of
COMBINE sodium and chlorine Na +1 Cl -1 To combine, we must make the charges = zero NaCl To name: use the names of the ions Sodium chloride
COMBINE calcium and bromine Ca +2 Br -1 We will need 2 bromine ions to match the +2 of calcium Ca Calcium bromide Br 2
COMBINE magnesium and nitrogen Mg +2 N -3 Can use least common denominator. 6 Mg 3 N 2 magnesium nitride
COMBINE magnesium and nitrogen Mg +2 N -3 Mg 3 N 2 magnesium nitride Flip flop the charges and turn them into subscripts.
Ion formation shortcuts
If charges are the same number drop charges and put symbols together.
The charges cancel out and become ZERO.
If charges are different numbers criss- cross the charge numbers and make a subscript on other ion.
Polyatomics??? K +1 SO 4 -2 Remember, in a Polyatomic ion all the atoms act as one, even the subscripts. If they are already there, they stay there! K 2 SO 4 potassium sulfate COMBINE potassium and sulfate
COMBINE aluminum and sulfate Al +3 SO 4 -2 Al 2 SO 4 3 ( ) aluminum sulfate How do we separate the subscripts so they look separate?
Practice problems 1. Ammonium and chlorine 2. Aluminum and selenate 3. Lead II and bicarbonate 4. Mercury I and phosphate
answers 1. NH 4 Cl Ammonium chloride 2. Al 2 (SeO 4 ) 3 Aluminum selenate 3. Pb(HCO 3 ) 2 Lead II bicarbonate 4. (Hg 2 ) 3 (PO 4 ) 2 Mercury I phosphate