Valence
Electrons:
ELECTRONS
AVAILABLE
FOR
BONDING
Definition
Valence electrons are electrons in
the outmost shell (energy level).
They are the electrons available
for bonding.
Group 1 (alkali metals) have 1
valence electron
Group 2 (alkaline earth metals)
have 2 valence electrons
Group 13 elements have 3
valence electrons
Group 14 elements have 4
valence electrons
Group 15 elements have 5
valence electrons
Group 16 elements have 6
valence electrons
Group 17 (halogens) have 7
valence electrons
Group 18 (Noble gases) have 8
valence electrons, except
helium, which has only 2
Transition metals (“d” block)
have 1 or 2 valence electrons
Lanthanides and actinides
(“f” block) have 1 or 2 valence
electrons
Dot Notations
An atom’s valence electrons can be represented
by Lewis dot notations.
1 valence e-
2 valence e-
3 valence e-
4 valence e-
X
X
X
X
5 valence e-
6 valence e-
7 valence e-
8 valence e-
X
X
X
X
Dot Notations – Period 2
Lewis dot notations for the valence electrons of
the elements of Period 2.
lithium
beryllium
boron
carbon
Li
Be
B
C
nitrogen
oxygen
fluorine
neon
N
O
F
Ne
Ionic Bonding
Bonds
 Forces that hold groups of atoms
together and make them function
as a unit.
 Ionic bonds – transfer of electrons
 Covalent bonds – sharing of
electrons
The Octet Rule – Ionic Compounds
Ionic compounds form so that each atom, by gaining or
losing electrons, has an octet of electrons in its highest
occupied energy level.
Metals lose electrons to form positively-charged cations
Nonmetals gains electrons to form negatively-charged
anions
Ionic Bonding:
The Formation of Sodium Chloride
 Sodium has 1 valence electron
 Chlorine has 7 valence electrons
 An electron transferred gives
each an octet
Na: 1s22s22p63s1
Cl: 1s22s22p63s23p5
Ionic Bonding:
The Formation of Sodium Chloride
This transfer forms ions, each with an
octet:
Na+ 1s22s22p6
Cl- 1s22s22p63s23p6
Ionic Bonding:
The Formation of Sodium Chloride
The resulting ions come together due to
electrostatic attraction
(opposites attract):
+
Na
Cl
The net charge on the compound must
equal zero
Examples of Ionic compounds
Mg2+Cl-2
Magnesium chloride: Magnesium loses two
electrons and each chlorine gains one
electron
Na+2O2-
Sodium oxide: Each sodium loses one
electron and the oxygen gains two electrons
Al3+2S2-3
Aluminum sulfide: Each aluminum loses
two electrons (six total) and each sulfur
gains two electrons (six total)
Metal
Lithium
Sodium
Potassium
Magnesium
Calcium
Barium
Aluminum
Monatomic
Cations
Li+
Na+
K+
Mg2+
Ca2+
Ba2+
Al3+
Ion name
Lithium
Sodium
Potassium
Magnesium
Calcium
Barium
Aluminum
Nonmetal
Ion Name
Fluorine
Monatomic
Anions
F-
Chlorine
Cl-
Chloride
Bromine
Br-
Bromide
Iodine
I-
Iodide
Oxygen
O2-
Oxide
Sulfur
S2-
Sulfide
Nitrogen
N3-
Nitride
Phosphorus
P3-
Phosphide
Fluoride
Sodium Chloride Crystal Lattice
Ionic compounds form solid
crystals at ordinary
temperatures.
Ionic compounds organize in a
characteristic crystal lattice of
alternating positive and
negative ions.
All salts are ionic compounds and form crystals.
Properties of Ionic Compounds
Structure:
Crystalline solids
Melting point: Generally high
Boiling Point:
Generally high
Electrical
Excellent conductors,
Conductivity: molten and aqueous
Solubility in
Generally soluble
water:
Ionic Compound Formulas
www.lab-initio.com
Ions
Cation: A positive ion
Mg2+, NH4+
Anion: A negative ion
Cl-, SO42-
Predicting Ionic Charges
Group 1:
H+
Lose 1 electron to form 1+ ions
Li+
Na+
K+
Predicting Ionic Charges
Group 2:
Be2+
Loses 2 electrons to form 2+ ions
Mg2+
Ca2+
Sr2+
Ba2+
Predicting Ionic Charges
Group 13:
B3+
Al3+
Ga3+
Loses 3
electrons to form
3+ ions
Predicting Ionic Charges
Neither! Group 13 elements
rarely form ions.
Lose 4
electrons or gain
4 electrons?
Group 14:
Predicting Ionic Charges
N3- Nitride
P3- Phosphide
As3- Arsenide
Gains 3
electrons to form
3- ions
Group 15:
Predicting Ionic Charges
O2S2Se2-
Oxide
Sulfide
Selenide
Gains 2
electrons to form
2- ions
Group 16:
Predicting Ionic Charges
F1-
Fluoride
Cl1-
Chloride
Group 17:
Br1-
Gains 1
electron to form
Bromide1- ions
I1-
Iodide
Predicting Ionic Charges
Group Stable
18: Noble
gases do not form ions!
Predicting Ionic Charges
Groups 3 - 12:
Iron(II) = Fe2+
Many transition elements have
more than one possible oxidation state.
Iron(III) = Fe3+
Predicting Ionic Charges
Groups 3 Some
- 12: transition elements
have only one possible oxidation state.
Zinc = Zn2+
Silver = Ag+
Writing Ionic Compound Formulas
Example: Barium nitrate
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than
one of a polyatomic ion.
Ba2+
(NO)3- 2
balanced!
Writing Ionic Compound Formulas
Example: Ammonium sulfate
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one
of a polyatomic ion.
+
( NH4)
2
SO42-
Not balanced!
Writing Ionic Compound Formulas
Example: Iron(III) chloride
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one
of a polyatomic ion.
Fe3+ ClNot balanced!
3
Writing Ionic Compound Formulas
Example: Aluminum sulfide
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than
one of a polyatomic ion.
3+
Al
2
2S
Not balanced!
3
Writing Ionic Compound Formulas
Example: Magnesium carbonate
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
2+
Mg
CO32-
They are balanced!
Writing Ionic Compound Formulas
Example: Zinc hydroxide
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than
one of a polyatomic ion.
Zn2+ ( OH) Not balanced!
2
Writing Ionic Compound Formulas
Example: Aluminum phosphate
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3+
Al
3PO4
They ARE balanced!
Naming Ionic Compounds
Cation first, then anion
Monatomic cation = name of the element
Ca2+ = calcium ion
Monatomic anion = root + -ide
Cl- = chloride
CaCl2 = calcium chloride
Naming Ionic Compounds
(continued)
Metals with multiple oxidation states
 some metal forms more than one cation
 use Roman numeral in name
 PbCl2
 Pb2+ is cation
 PbCl2 = lead(II) chloride
Complete These Reviews
(They are due before class is over!!!!!!!!!)
• Monatomic Ions
(http://www.sciencegeek.net/Chemistry/Quiz
zes/MonatomicIons/)
• Simple Ion Formulas
(http://www.sciencegeek.net/Chemistry/taters/
Unit2IonicCompoundFormulas.htm)