Ionic Formulas
Turning chemistry into algebra
REVIEW
• We can tell how many electrons an atom will
gain or lose by looking at its valence electrons.
• Metals like to lose electrons. (Cations)
– Ex. Na +
• Nonmetals like to gain electrons. (Anions)
– Ex: O 2-
• All elements try to have a full valence of 8
electrons(OCTET RULE).
Chemical Bonding
A chemical bond is the force of attraction
that holds two atoms together.
Cl
Na
Attractive Force
Why do elements form chemical
bonds?
Atoms form chemical bonds in order to
fill their outermost energy level with
electrons.
• A full valence causes an atom to be more
stable.
•A full valence consists of 8 valence electrons.
Ionic Bonding
Ionic bonds: Metal atoms transfer
electrons to nonmetal atoms. Producing
oppositely charged ions (cation & anion)
which attract each other.
Na + +
Cl-

NaCl
Write an ionic formula for
+
−
Na bonding with F
Balance the charges.
Na+
F−
(1+) + (1-) = 0
1 Na+ and 1 F− = NaF
Write an ionic formula for
+
2−
K bonding with S
Balance the charges.
K+
S2−
+
K
2(1+) + (2-) = 0
2 K+ and 1 S2− = K2S
Write an ionic formula for
3+
-2
Fe bonding with O
Balance the charges.
Fe3+
O−2
Fe3+
O−2
O−2
2(3+) + 3(2-) = 0
2 Fe3+ and 3 O−2 = Fe2O3
Write the formula for…
an ionic compound composed of:
3+
Al
and
2S
Al2S3
Write the formula for…
an ionic compound composed of:
2+
Cd
and
CdF2
F
Write the formula for…
an ionic compound composed of:
+
Ag
and
2O
Ag2O
Write the formula for…
an ionic compound composed of:
2+
Pb
and
Br
PbBr2
Write the formula for…
an ionic compound composed of:
2+
Hg
and
3P
Hg3P2