WHY DO
ATOMS
BOND?
Why do atoms form bonds?
Atoms need to be stable
Stable = full outer energy level
Octet Rule
Full = 8 electrons
(except level 1 full = 2 electrons)
Ex. Neon
Ne
Helium
He
Learning Objective
To understand covalent bonding
Electron arrangement in outer shells
1
8
H
He
2
3
4
5
6
7
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
Ar
K
Ca
To understand covalent bonding
Look at Na and Cl
1
8
H
He
2
3
4
5
6
7
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
Ar
K
Ca
EXAMPLE
Sodium + Chlorine
(2,8,1)
(2,8,7)
Sodium +
Chlorine
Sodium
Chloride
00
X
Na
0
Cl 00
00
[ Na] + 0
X
00
00
Cl
00
ION (charged particle)
Na
11
11
23
23
particles number
+
Na
charge
protons
11
+
Proton
electrons
11
-
Electron
#
11
11
neutrons
12
0
Neutron
12
Neutral atom
charge
Lose
1
11
10
+1
Ion
Atom that has lost or
gained electrons
Atom with a charge
Ca+ion
positive ion
metals
Ca+2
ex.
*superscript shows charge
Anion
ex.
negative ion
nonmetal
Cl-1
Electron arrangement
• Worksheet (top, left)
Atom
Electron
Arrangement
Lose or gain
electrons?
Ion Symbol
Li
2.1
lose 1
Li+
N
2.5
gain 3
N3O
Na How can you tell if the atom
Mgwill gain or lose electrons?
P
S
Cl
K
Ca
EXAMPLE
Sodium + Chlorine
(2,8,1)
(2,8,7)
Sodium +
Chlorine
Sodium
Chloride
00
X
Na
0
Cl 00
00
[ Na] + 0
X
00
00
Cl
00
Atom
Electron
Arrangement
Lose or gain
electrons?
Ion Symbol
Li
N
O
Na
Mg
P
S
Cl
K
Ca
2.1
2.5
lose 1
gain 3
Li+
N3-
To understand covalent bonding
Look at cations vs anions
1
8
H
He
2
3
4
5
6
7
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
Ar
K
Ca
Ion
Atom that has lost or
gained electrons
Atom with a charge
Ca+ion
positive ion
ex.
metals
Ca+2
*superscript shows charge
Anion
ex.
negative ion
nonmetal
Cl-1
You must follow the
rules!
Naming Ions
Cations
use the element name
ex. Calcium
 calcium
Anions
take element name and change
the ending to –ide
ex.
Chlorine
Bromine
 chloride
 bromide
Look at Mg and O
1
8
H
He
2
3
4
5
6
7
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
Ar
K
Ca
Magnesium + Oxide
(12Mg 2,8,2) (8O 2,6)
O
Mg
[Mg]
Magnesium
Oxide
2+
[ ]
O
2-
IONIC BONDING
•metal atoms give (lose) electrons and
non-metal atoms take (gain) electrons
results in ions
•Ions bond together by the attraction of (+)
and (–) charges
•The new compound has no overall charge
(is neutral) because there is the same
amount of (+) and (–) charges
BONDING = STABILITY
8 IS GREAT!
A covalent bond exists when two electrons are
shared by two non-metallic atoms.*
To understand covalent bonding
Look at Ca and Cl
1
8
H
He
2
3
4
5
6
7
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
Ar
K
Ca
CaCl2
[ ]
[ ]
Cl
Cl
[Ca]2+
Ca
Cl
Cl
CROSSOVER RULE TO FIND FORMULAE
1. Write the name and
symbol of the ions
4+
2-
2. Write the valencies
3. Crossover the
valencies and reduce
4. Write the formula
using a subscript to
indicate the number of
each ion
• Backside of “Parlez-Vous chemistry” workheet
the elements listed below. Write the name and formula
of the element in your note book.
ACTIVITY: IONIC BONDING
1. magnesium & bromine
2. lead & nitrate
3. lithium & sulfate
4. copper & hydroxide
5. potassium & oxygen
6. ammonium & sulfate
7. sodium & phosphate
8. silver & chlorine
9. iron (III) & oxygen
10.zinc & carbonate
11. lead and iodine
12. aluminum & hydroxide
13. calcium & phosphate
14. sodium & hydrogen
carbonate
15. iron (II) & sulfate
16. potassium & sulfur
17. lithium & bromine
18. silver & nitrate
19. copper & carbonate
20. ammonium & chloride
PART A. Form the different ionic compounds listed above.
PART B. Make a new ionic compound using the “ion pieces”. Form at least
5 new compounds, and write the chemical name and formula for
each compound.
PART C. Research on the 5 new compounds by finding its:
description and use/importance
SUMMARY: Ionic Bonding
• Is when atoms gain or lose up to 3 electrons to get a full valence
shell
• When they do this they become ions
• An ion is an electrically charged atom i.e. there are more or less
electrons than protons e.g. Metals in Group 1, 2 and 3 lose
electrons and become positively charged: Mg2+ Na+ Al3+
•Non-metals in Group 5, 6 and 7 gain electrons to become negatively
charged: F- P3- S2•Ions in a compound are held together by the attraction of (+) and (–)
charges
•The compound has no overall charge because there is the same
amount of (+) and (–) charges