Unit 8: Covalent Bonding

Octet rule

Atoms will lose, gain, or share electrons to achieve configurations of eight valence electrons

Covalent bond

Chemical bond formed from the sharing of valence electrons

Which type of elements does covalent bonding occur between?

Nonmetals

Molecule

A group of two or more atoms that are bonded covalently

Diatomic molecules

Atoms that pair up in nature rather than exist as the single atom

7 diatomic molecules

• H₂

• N₂

• O₂

• F₂

• Cl₂

• Br₂

• I₂

Bond length

Distance between atoms in a bond

Nomenclature rules for binary molecules

1. The first element in the formula is always named first and uses the entire element name

2. The second element uses the root of the name with the suffix “-ide“

3. Prefixes are used to indicate the number of atoms of each type in the compound

Mono-

1

Di-

2

Tri-

3

Tetra-

4

Penta-

5

Hex-

6

Hepta-

7

Octa-

8

Nona-

9

Deca-

10

Which part of a molecules is more likely to be an exception to the octet rule?

Central atom

Electron deficient

When there is an insufficient number of electrons to complete the octet of the central atom

Expanded octet

When an atom can take more than 8 electrons around it (more than an octet)

What is the relationship between covalent bond length and strength?

Short bond length= higher bond strength

Multiple bonds make bond lengths ____

shorter

Bond dissociation energy

The energy required to break a specific covalent bond

Electron affinity trend

Increases across a period, decreases down a group

Polar bonds

When electrons are not shared equally causing an unequal distribution of charge

What makes a molecules polar?

• Difference in electronegativities between the atoms

• Arrangement of the atoms has to be unsymmetrical

Nonpolar molecules

Molecules with bonds where atoms have similar electronegativities

Molecules with polar bonds but that are overall symmetrical are also ____

nonpolar

Do polar and nonpolar molecules mix?

No