Chemical element · reference page

Nitrogen

Nitrogen is element 7 (N), located in period 2, group 15 and the p block. At room temperature its reference phase is gas. Its electron configuration is [He] 2s2 2p3.

Atomic number7

Standard atomic weight[14.00643, 14.00728]

Group15

Period2

Blockp

Electron configuration[He] 2s2 2p3

Electronic structure

What controls its chemistry

Group 15 atoms have five valence electrons. They can form three covalent bonds, participate in multiple bonding, or adopt several oxidation states depending on the element and its bonding partners.

The configuration [He] 2s2 2p3 places nitrogen in this family, but the chemistry changes markedly from non-metallic nitrogen and phosphorus to the heavier, more metallic members.

Chemical forms

Compounds, ions and materials

Common families include hydrides, oxides, oxoacids or oxoanions, halides and compounds with metals. Oxidation states from −3 to positive values occur across the group, with the accessible range changing strongly from nitrogen to bismuth.

Physical behaviour

State and phase changes

The reference phase at room temperature is gas. The listed density is 1.251 g/L. The melting point is 63.17 K (-210.0 °C). The boiling point is 77.36 K (-195.8 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where nitrogen is found and used

In practice, nitrogen is encountered in the atmosphere, fertiliser production and cryogenics.

In practice

Examples of real uses

The atmosphere

Nitrogen is present naturally in air or atmospheric compounds and important to atmospheric chemistry.

Fertiliser production

Nitrogen is part of fertiliser chemistry or the industrial processes used to supply essential plant nutrients.

Cryogenics

Nitrogen is used at very low temperatures as a coolant, working fluid or material whose low-temperature behaviour is useful.

Periodic position

What its neighbours tell us

Nitrogen is in period 2 and group 15. In the neighbourhood shown here, it lies between carbon and oxygen in the same period; phosphorus is directly below it in the same group. These positions make it possible to compare atomic size, ionisation energy and bonding behaviour with nearby elements.

Reference data

Physical and atomic properties

Classificationdiatomic nonmetal

Phase at room temperatureGas

Electron shells2 · 5

Density1.251 g/L

Melting point63.17 K (-210.0 °C)

Boiling point77.36 K (-195.8 °C)

Pauling electronegativity3.04

First ionisation energy1 402 kJ/mol

Electron affinity—

Values describe the element or neutral atom where applicable. Physical data can depend on allotrope, pressure and measurement conditions.

History

Discovery and identification

The discovery of nitrogen is associated with Daniel Rutherford. Recognition of the element, isolation of a pure sample and assignment of its modern atomic number did not necessarily occur at the same time.

Isotopes and atomic weight

How isotope composition changes the numbers

The standard atomic weight is given as the interval [14.00643, 14.00728]. Natural samples can differ slightly in isotope proportions, so a single universal decimal value would hide real variation between materials.

Nitrogen has at least one stable isotope. Different isotopes have the same number of protons and therefore the same element identity, but different neutron numbers and atomic masses.

Safety

Handling and exposure

The gas is not necessarily chemically toxic, but it can displace oxygen in confined spaces. Ventilation and oxygen monitoring matter in bulk handling.