Title: Covalent bonding
1Covalent bonding
- Covalent bond A chemical bond formed when two
atoms share electrons.
2Covalent bonding
- Covalent bond A chemical bond formed when two
atoms share electrons. - Co means together, joint, jointly.
3Covalent bonding
- Covalent bond A chemical bond formed when two
atoms share electrons. - Co means together, joint, jointly.
- Double bond When two pairs of electrons are
shared between atoms.
4Covalent bonding
- Covalent bond A chemical bond formed when two
atoms share electrons. - Co means together, joint, jointly.
- Double bond When two pairs of electrons are
shared between atoms. - Molecular compounds Molecules formed through
covalent bonding.
5Electron dot diagram
6Electron dot diagram
- C O H N F
- Review What number of valence electrons do atoms
want in order to be stable?
7Electron dot diagram
- C O H N F
- Review What number of valence electrons do atoms
want in order to be stable? - Answer 0 or 8
8Electron dot diagram
- C O H N F
- Atoms want 0 or 8 valence electrons to be stable.
- However, there are two exceptions hydrogen and
helium. They are stable when their inner shell of
2 is filled.
9- Atoms want 0 or 8 valence electrons to be stable.
However, there are two exceptions hydrogen and
helium. They are stable when their inner shell of
2 is filled.
Helium
10Helium
Thus hydrogen only needs one more valence
electron to be stable. Helium is already stable.
11Examples of covalent bonds/molecular compounds
12Examples of covalent bonds/molecular compounds
F2
13Examples of covalent bonds/molecular compounds
F2
14Examples of covalent bonds/molecular compounds
F2
15Examples of covalent bonds/molecular compounds
F F O H H
F2
Water molecule H20
16Examples of covalent bonds/molecular compounds
O
17Examples of covalent bonds/molecular compounds
O O
18Examples of covalent bonds/molecular compounds
O O
Oxygen molecule O2 (double bond)
19Examples of covalent bonds/molecular compounds
O O
Oxygen molecule H20 (double bond)
H3N
20Examples of covalent bonds/molecular compounds
O O
Oxygen molecule H20 (double bond)
N
H3N
21Examples of covalent bonds/molecular compounds
O O
Oxygen molecule H20 (double bond)
H
N
H
H3N
H
22Examples of covalent bonds/molecular compounds
C02
23Examples of covalent bonds/molecular compounds
C02
C
24Examples of covalent bonds/molecular compounds
C02
O
C
25Examples of covalent bonds/molecular compounds
C02
O
C
O
26Examples of covalent bonds/molecular compounds
C02
O
C
O
double bond
27Examples of covalent bonds/molecular compounds
N2
N
28Examples of covalent bonds/molecular compounds
N2
N
29Examples of covalent bonds/molecular compounds
N2
N
N
30Examples of covalent bonds/molecular compounds
N2
N
N
triple bond (this is the maximum number of bonds
possible)
31More aboutmolecular compounds
- Atoms in molecular compounds do not have strong
plus-minus charges. - Thus less heat is needed to melt or boil
molecular solids. - Salt (an ionic compound) melts at 801 C. Sugar
(a molecular compound) melts at 185 C.
32- Because electrons do not move between the atoms,
molecular compounds do not conduct electricity
well.
33- Because electrons do not move between the atoms,
molecular compounds do not conduct electricity
well. - This includes compounds such as rubber and
water, which do not conduct electricity.
34Polar molecular compounds
- Some atoms pull more strongly on the shared
electrons than other atoms do.
35Polar molecular compounds
- Some atoms pull more strongly on the shared
electrons than other atoms do. - As a result, the valence electrons move closer
to the stronger atoms.
36Polar molecular compounds
- Some atoms pull more strongly on the shared
electrons than other atoms do. - As a result, the valence electrons move closer
to the stronger atoms. - Since electrons have a negative charge, the
strong atom will now have a slightly negative
charge, and the weaker atom a slightly positive
charge.
37Nonpolar bond
Equal pull
38Polar bond
-
Unequal pull
39Water is a polar bond
- Electrons are
- pulled toward
- the oxygen
- atom.
40Water is a polar bond
- Electrons are
- pulled toward
- the oxygen
- atom.
- This causes cohesion The attraction that occurs
between particles of the same substance.
41Can you think of examples of waters cohesion
(holding together)?
42Can you think of examples of waters cohesion
(holding together)?
Water droplets
43Can you think of examples of waters cohesion
(holding together)?
Surface tension
44Can you think of examples of waters cohesion
(holding together)?
Water transport in plants http//www.youtube.com/
watch?vCT4pURpXkbY
45Why dont oil and water mix?
46Why dont oil and water mix?
- The polar water molecules are attracted more
strongly to each other than they are to the
nonpolar oil molecules.
47Why dont oil and water mix?
- The polar water molecules are attracted more
strongly to each other than they are to the
nonpolar oil molecules. - Soap molecules are polar on one end and nonpolar
on the other.
48Why dont oil and water mix?
- The polar water molecules are attracted more
strongly to each other than they are to the
nonpolar oil molecules. - Soap molecules are polar on one end and nonpolar
on the other.