1. CHAPTER 7
Bonding
7.1 What is a Chemical Bond?

2. We also know that electrons are responsible for chemical bonding.
Protons (+)
There is an equilibrium in attractive and repulsive forces inside the atom
Neutrons (0)
Electrons (-)
We also know that electrons are responsible for chemical bonding.

3. Is a chemical bond really a “stick” between two atoms?

4. Is a chemical bond really a “stick” between two atoms?
No:
The binding force between two atoms is an equilibrium of several forces.

5. That distortion is called polarization.
The electron cloud responds to changes in the electromagnetic environment.
That distortion is called polarization.

6. What happens when two hydrogen atoms approach each other?

7. What happens when two hydrogen atoms approach each other?
Each nucleus attracts the electron cloud of the other atom.
Each nucleus repels the other nucleus.
The electron cloud repels the other electron cloud.

8. What happens when two hydrogen atoms approach each other?
Each nucleus attracts the electron cloud of the other atom.
Each nucleus repels the other nucleus.
The electron cloud repels the other electron cloud.
At a certain distance there is an equilibrium between attractive and repulsive forces.

9. If the distance is close enough, an electron can be transferred or shared.
A chemical bond forms.
At a certain distance there is an equilibrium between attractive and repulsive forces.

10. A covalent bond An ionic bond
Electrons are shared between the two nuclei.
One or more electrons are transferred to form ions.
The positive and negative ions attract each other.

11. Molecular models are approximations of the real thing.
Representation
Water (H2O)
Molecular models are approximations of the real thing.

12. Electrons are unevenly shared between oxygen and hydrogen.
Some atoms are more greedy for electrons than others!
Electrons are unevenly shared between oxygen and hydrogen.

13. Molecular surfaces colored by charge
Hydrogen, H2
Water, H2O
Electrons are equally shared between the hydrogen atoms
There are more electrons on the oxygen side than on the hydrogen side

14. Electronegativity
electronegativity: the relative affinity of an element for electrons from other atoms. Higher electronegativity means stronger attraction for electrons.

15. Oxygen is slightly more electronegative than hydrogen.
Electronegativity
(electron sharing)
Oxygen is slightly more electronegative than hydrogen.
This results in uneven sharing of electrons.

16. Ionization Energy
ionization energy: the energy required to completely remove an electron.

17. Nonpolar covalent bond
Types of bond
Nonpolar covalent bond
Atom 1
Atom 2
Difference in EN
Electron sharing
high EN
very little
equal or nearly equal sharing
EN = electronegativity

18. Nonpolar covalent bond
Types of bond
Nonpolar covalent bond
Polar
covalent bond
Atom 1
Atom 2
Difference in EN
Electron sharing
high EN
very little
equal or nearly equal sharing
high EN
medium EN
moderate
uneven sharing
EN = electronegativity

19. Nonpolar covalent bond
Types of bond
Nonpolar covalent bond
Polar
covalent bond
Ionic bond
Atom 1
Atom 2
Difference in EN
Electron sharing
high EN
very little
equal or nearly equal sharing
high EN
medium EN
moderate
uneven sharing
high EN
low EN
large
transfer of electrons
EN = electronegativity

20. Types of bond

21. Types of bond
An ionic crystal
Ionic bonds connect atoms to all neighbors, not just a single neighbor as in a molecule.

22. Types of bond A metallic bond Like a covalent bond
Like an ionic bond
Electrons are shared
No two atoms are specifically bonded together
metallic bond: an attraction between metal atoms that loosely involve many electrons.

23. Nonpolar covalent bond
Ionic bond
Difference in EN
Electron sharing
very little
equal or nearly equal sharing
moderate
uneven sharing
large
transfer of electrons
We can determine the bond type from the difference in electronegativity.
EN = electronegativity

25. Nonpolar covalent bond
Ionic bond
Difference in EN
Electron sharing
very little
equal or nearly equal sharing
moderate
uneven sharing
large
transfer of electrons
EN = electronegativity

27. Electronegativity of atoms:
Difference in electronegativity:
I – I = 2.66 – 2.66 = 0

28. The I–I bond is nonpolar covalent.
Electronegativity of atoms:
I = 2.66
Difference in electronegativity:
I – I = 2.66 – 2.66 = 0
The I–I bond is nonpolar covalent.

29. Electronegativity
of atoms:
C = 2.55
O = 3.44
Difference in electronegativity:
O – C = 3.44 – 2.55 = 0.89

30. The C–O bond is polar covalent.
Electronegativity
of atoms:
C = 2.55
O = 3.44
Difference in electronegativity:
O – C = 3.44 – 2.55 = 0.89
The C–O bond is polar covalent.
0.89

31. A phospholipid molecule
Most molecules contain more than two atoms and more than one bond.
Some polar bonds
All nonpolar bonds
A phospholipid molecule
(found in cell membranes)

32. Nonpolar bonds in a molecule make the molecule nonpolar.

33. Polar bonds in a molecule make the molecule polar.

34. Nonpolar covalent bond
Types of bond
Nonpolar covalent bond
Polar
covalent bond
Ionic bond
Atom 1
Atom 2
Difference in EN
Electron sharing
high EN
very little
equal or nearly equal sharing
high EN
medium EN
moderate
uneven sharing
high EN
low EN
large
transfer of electrons
EN = electronegativity