How elements exist

The noble gases (Group 18) are the only elements that exist as isolated atoms. Atoms of argon are shown.

The particles in most elements have two or more atoms joined by attractive forces known as chemical bonds. Bonds between atoms in elements are either metallic or covalent.

Copper (Cu)

Metals exist as lattices with metallic bonding between the atoms.

Lattices are ordered arrangements that extend infinitely in all directions.

A small portion of a copper lattice is shown.

	Group 17 halogens
	F₂
	Cl₂
	Br₂
	I₂

Nonmetallic elements may exist as atoms, molecules or network solids.

Molecules are discrete particles containing two or more atoms joined by covalent chemical bonds.

The elements nitrogen, oxygen and hydrogen exist as diatomic molecules (N₂, O₂, H₂) as do all elements in Group 17 (see right).

Network solids are infinite lattices with atoms linked by covalent bonds.

Diamond, one form of elemental carbon, has the lattice shown below.

A second form, graphite, has a diffferent arrangement of carbon atoms.

Allotropes are different physical forms of the same element.

Graphite and diamond are allotropes of carbon.
The molecules O₂and O₃(ozone) are also allotropes.