1. 6.2 Covalent Bonding Key Concepts:
1. How are atoms held together in a covalent bond?
2. What happens when atoms don’t share electrons equally?
3. What factors determine whether a molecule is polar?
4. How do attractions between polar molecules compare to attractions between nonpolar molecules?

2. I. Covalent Bonds A. Electrons are shared in a covalent bond.
B. Bonds are usually between
nonmetals.
C. Atoms can share 1, 2, or 3 pairs
of electrons, so called single,
double, or triple bond.

3. D. Models
1. Ball and stick model a. Each ball represents an atom. b. Each stick represents a bond, that shows bond length and angle. c. 3-D model *Use flexible springs to show that bonds can stretch, bend or rotate.

4. D. Models 2. Structural formula a. Symbols of the atoms are
used to show where bonds
are located.
b. 2D model

5. D. Models 3. Space filling model a. Shows the relative
sizes of atoms in
a compound.
b. 3D model

6. D. Models 4. Electron cloud model a. Shows that the orbitals
of the atoms overlap
when a covalent bond
forms.
b. 2D model

7. E. Molecules of Elements
1. Molecule is a neutral group of atoms that are joined by one or more covalent bonds.
2. The attractions between the shared electrons and protons in each nucleus hold the atoms together.
3. Diatomic molecules- many nonmetal elements exist as two atoms bonded covalently.

8. II. Unequal Sharing of Electrons
A. General Trends
1. Elements on the right side of the periodic table have a greater attraction for electrons than elements on the left side.
2. Elements at the top of a group have a greater attractions for electrons than elements at the bottom of a group.

9. B. Polar Covalent Bonds
1. Molecule of an element- shared electrons are attracted equally to the nuclei of both atoms- called a nonpolar
covalent bond
2. Molecule of a compound- electrons may not be shared equally- called a polar covalent bond.

10. B. Polar Covalent Bond
3. When atoms form polar covalent bond, the atom with the greater attraction for electrons has a partial negative charge.
The other atom has a partial positive charge.

11. B. Polar Covalent Bonds
a. In a hydrogen chloride molecule, the shared electrons spend more time near the chlorine atom than near the hydrogen atom.
b. Shared electrons in a hydrogen chloride molecule spend less time near the hydrogen atom than near the chlorine atom.

12. C. Polar and Nonpolar Molecules
1. Depends upon
a. type of atoms in the molecule and
b. shapes of the atoms in the molecules.

13. C. Polar and Nonpolar Molecules
2. In a carbon dioxide (CO2) molecule, the polar bonds between the carbon atom and the oxygen atoms cancel out because the molecule is linear.
a. Double bonds between oxygen and carbon.
b. Oxygen has greater attraction for electrons, so each double bond is polar.
c. The pulls on the electrons from opposite directions are equal.
d. The pulls cancel out and the molecule as a whole is nonpolar.

14. C. Polar and Nonpolar Molecules
3. In a water (H2O) molecule, the polar bonds between the oxygen atom and the hydrogen atoms do not cancel out because the molecule is bent.
a. Two single bonds between oxygen and hydrogen.
b. The bonds are polar because oxygen has a
greater attraction for electrons.
c. The water molecule is bent, the polar bonds do not cancel.
d. The oxygen side of the molecule has a partial negative charge. The hydrogen side has a partial positive charge.

15. III. Attractions Between Molecules
A. Molecular Compounds
1. There are forces of
attraction between molecules,
2. But not as strong as ionic or covalent compounds.

16. III. Attractions Between Molecules
B. Polar vs. Nonpolar
1. Attractions are stronger between polar molecules than between nonpolar molecules.
2. Water is polar and has a boiling point of 100C, whereas
3. Methane (about the same mass as water) is nonpolar and has a boiling point of C.

17. 6.2 Assignment 6.2 Review p. 169 #1-8 all