Vocabulary

Chemical Bond
– attractive force between atoms or ions that
binds them together as a unit
– bonds form in order to…
 increase stability
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Chemical Bonding
atoms give up or gain electrons and are attracted
Na loses an e–
Na  Na1+ + e–
(Metal)
ionic compounds = salts
Cl gains an e–
Cl + e–  Cl1–
(Non-Metal)
Na1+ + Cl1–  NaCl
K1+ + NO31–  KNO3
where NO31– is a polyatomic ion: a charged group of atoms
that stay together
Ionic Bonding
NaCl
n=3
-
n=2
n=3
-
-
-
-
-
-
-
Na
[Ne]3s1
-
-
-
+
-
-
-
-
-
-
-
-
-
Cl
[Ne]3s23p5
-
-
-
Na+
[Ne]
-
-
-
Cl[Ne]3s23p6
Transfer of electrons to achieve a stable octet (8 electrons in valence shell).
Properties of Ionic Compounds
VERY HARD
each ion is bonded to several oppositelycharged ions
HIGH MELTING POINTS
many bonds must be broken
BRITTLE
with sufficient force, like atoms are brought
next to each other and repel
Writing Chemical
Formulas
The Swap n Drop Method



The Swap n Drop method is an easy way to determine
the formula of any ionic compound.
The ionic compound can be the simple (binary) ionic
compound with just two elements, or one that has a
polyatomic ion as part of it.
You can get the oxidation values directly off of the
periodic table for most elements or they are part of the
“Polyatomic Cheat Sheet”.
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a
2 & 4 together.
Calcium and Nitrogen
1. Ca
N
2.
3.
Ca2+
Ca3N2
N3-
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Be
Br
Br
1.
Be
2.
Be2+
3.
BeBr2
Br1-
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Lithium Oxide:
1. Li
O
2.
3.
Li1+
Li2O
O2-
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Magnesium Nitride:
1. Mg
N
2.
3.
Mg2+
Mg3N2
N3-
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Lithium Chloride:
1. Li
Cl
2.
3.
Li1+
LiCl
Cl1-
Formulas With Transition Metals



The Swap n Drop method is also used when dealing with
metals that have more than one oxidation number.
(Copper, Iron, Lead, or Tin)
The oxidation number for these metals can be found in
the name of the compound that contains them.
Examples:
– Iron (II) oxide – the Iron (Fe) used here has an oxidation
number of 2
– Lead (IV) sulfide – the Lead (Pb) used here has a oxidation
number of 4.
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Iron (III) Oxide:
1. Fe
O
2.
3.
Fe3+
Fe2O3
O2-
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Lead (II) Chloride:
1. Pb
Cl
2.
3.
Pb2+
PbCl2
Cl1-
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Copper (I) Phosphide:
1. Cu
P
2.
3.
Cu1+
Cu3P
P3-
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Tin (II) Sulfide:
1. Sn
S
2.
Sn2+
3.
Sn2S2
4.
SnS
S2-
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Lead(IV) Oxide:
1. Pb
O
2.
Pb4+
3.
Pb2O4
4.
PbO2
O2-
Polyatomic Ions

.
Polyatomic ions are clusters of atoms that
stay together as one unit and carry an
overall charge. Most polyatomic ions are
negatively charged.
Polyatomic Ionic Compounds
Parenthesis
 You need more than one polyatomic ion in your formula…This
means that you will have to use brackets. Use parenthesis
whenever you need more than one polyatomic ion in the formula.
 Example: Iron (III) nitrate…
– Start with symbols and combining capacities…
Fe3
NO31
– After the Swap n Drop, you may get one of two possibilities…
 FeNO33


OR
Fe (NO3)3
The second option is right because it says you need two nitrate
clusters to go with every iron atom. The first option, which did not
use reads as one iron atom and thirty-three oxygen atoms.
Fe(NO3)3 is the correct formula! Use the parenthesis!
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Sodium Nitrate:
1. Na
NO3
2.
3.
Na1+
(NO3)1-
Na(NO3)
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Calcium Chlorate
1. Ca
ClO3
2.
3.
Ca2+
(ClO3)1-
Ca(ClO3)2
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Lithium Phosphate:
1. Li
PO4
2.
3.
Li1+
(PO4)3-
Li3(PO4)
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Aluminum Sulfate:
1. Al
SO4
2.
3.
Al3+
(SO4)2-
Al2(SO4)3
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Tin (IV) Carbonate:
1. Sn
CO3
2.
3.
4.
Sn4+
(CO3)2-
Sn2(CO3)4
Sn(CO3)2
Reduce!
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Ammonium Phosphate:
1. NH4
PO4
2.
3.
( NH4)1+ ( PO4)3(NH4)3 ( PO4)
Swap it and Drop it
Steps (in order)
1. Write the chemical
symbols.
2. Write the oxidation
number over the
symbols.
3. Swap it and Drop it.
4. Reduce – if necessarythe same numbers or a 2
& 4 together.
Magnesium Carbonate:
1. Mg
CO3
2.
3.
4.
Mg2+
(CO3)2-
Mg2(CO3)2
Mg(CO3)
Reduce!