Nonmetals represent a diverse classification of elements that lack the characteristic properties of metals. Located predominantly on the right side of the periodic table, these elements are poor conductors of both heat and electricity, with the notable exception of carbon in its graphite form. In their solid state, nonmetals are typically brittle and dull, unable to be shaped or drawn into wires like their metallic counterparts. This category includes some of the most common substances in the universe.
Identifying the Two Most Common States
The physical states of nonmetals at standard room temperature and pressure are highly varied. While a few nonmetals can be found as solids, liquids, and gases, the vast majority exist in only two states: gases and solids. The state an individual nonmetal adopts is directly related to the strength of the forces holding its atoms or molecules together. Nonmetals with weak intermolecular forces exist as gases, while those that form robust, extended structures remain solids.
Nonmetals Found as Solids
A number of nonmetals form solids at room temperature due to strong, internal bonding arrangements. These solid nonmetals are generally brittle, lacking the malleability and ductility associated with metals. Carbon is a prime example, existing in allotropes such as diamond, where atoms are linked in a rigid, three-dimensional covalent network that gives it extreme hardness. Other solid nonmetals, like sulfur and phosphorus, form large, complex molecular structures that require significant energy to break apart. Iodine is another solid nonmetal that exists as a purplish-black crystalline solid, maintained by strong intermolecular forces.
Nonmetals Found as Gases
Gaseous nonmetals constitute the largest group by element count and are characterized by extremely weak intermolecular forces. Their boiling points fall far below standard room temperature, allowing them to remain in the gas phase. This group includes the elements that make up the bulk of Earth’s atmosphere, such as diatomic oxygen (\(\text{O}_2\)) and nitrogen (\(\text{N}_2\)), along with hydrogen, fluorine, and chlorine. The entire group of Noble Gases also falls into this category:
- Helium
- Neon
- Argon
- Krypton
- Xenon
- Radon
These gases exist as single, non-bonded atoms, resulting in the lowest boiling points of all elements.
The Notable Liquid Exception
The division of nonmetals into solids and gases at room temperature has only one elemental exception: bromine. Bromine is the sole nonmetal that exists as a liquid under standard conditions. It is a dense, reddish-brown element that readily evaporates to form a toxic gas. Its melting point (approximately \(-7.2^\circ\text{C}\)) and boiling point (around \(58.8^\circ\text{C}\)) conveniently bracket the average range of room temperature, placing the element distinctly in the liquid state. As a diatomic molecule (\(\text{Br}_2\)), its intermolecular forces are strong enough to maintain a liquid state, unlike the lighter halogens.