I. Allotropy

A. Definition

Property of an element to exist in different physical forms.

B. Allotropes

Different forms of the same element in the same physical state.

C. Characteristic

Same element atoms arranged in different manners.

II. Carbon Allotropes

A. Three important allotropes:

• 1. Graphite
• 2. Diamond
• 3. Buckyballs (C-60)

III. Graphite

A. Structure:

• 1. Flat two-dimensional layers
• 2. Hexagonally arranged carbon atoms
• 3. Each C-atom covalently bonded to three others

B. Inter-layer bonding:

• 1. Weak intermolecular bonds
• 2. Allows layers to slide over one another

C. Properties:

• 1. Soft and slippery
• 2. Good conductor of electricity

D. Application:

Used as a lubricant.

IV. Diamond

A. Structure:

• 1. Each C-atom covalently bonded to four others
• 2. Rigid network of tetrahedral shape
• 3. Three-dimensional arrangement

B. Properties:

• 1. Hardest crystalline allotrope of carbon
• 2. Very high melting point
• 3. Non-conductor of electricity

C. Reason for non-conductivity:

No free electrons.

V. Buckyballs (C-60)

A. Also known as fullerenes

B. Structure:

• 1. Football-like fused hollow ring
• 2. Composed of 20 hexagons and 12 pentagons
• 3. 60 carbon atoms, each bonded to 3 others