Nitrogen (N)

The N≡N triple bond is one of the strongest in chemistry, which is why nitrogen makes up 78% of the air and almost nothing happens to it. Breaking that bond industrially — the Haber-Bosch process, run at roughly 450 °C and 200 atmospheres — consumes on the order of 1-2% of world energy production, and the nitrogen in roughly half the protein in the human body has been through it. The same stubborn bond is why nitrogen compounds make good explosives: the products want to become N₂, and releasing that much bond energy at once is what an explosion is.

Properties

Atomic number

7

Symbol

N

Standard atomic weight

14.007 u

Category

Nonmetal

Group

15

Period

2

Block

p-block

Electron configuration

[He] 2s² 2p³

Electrons per shell

2, 5

Melting point

63.15 K — -210.0 °C — -346.0 °F

Boiling point

77.36 K — -195.8 °C — -320.4 °F

Density

0.0012506 g/cm³

Electronegativity

3.04 (Pauling)

Oxidation states

+5, +4, +3, +2, +1, -1, -2, -3

Discovered

1772 by Daniel Rutherford

Electron configuration

Full

1s² 2s² 2p³

Noble gas shorthand

[He] 2s² 2p³

Shells

K: 2 · L: 5

What it is used for

• Ammonia for fertiliser, which feeds roughly half the world
• Liquid nitrogen for freezing biological samples and food
• An inert blanket in food packaging, wine tanks and fuel systems
• Nitric acid for explosives, dyes and nylon
• Purging and pressure-testing pipework

Hazards

• Asphyxiation risk in confined spaces — it displaces oxygen without warning
• Liquid nitrogen at 77 K causes severe cold burns and can shatter sealed containers

IUPAC publishes an interval, [14.00643, 14.00728]; 14.007 is the conventional value. Density is the gas at 0 °C and 101.325 kPa; liquid nitrogen is 0.807 g/cm³.

Neighbours in the table

Group 15

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Nitrogen sits in group 15 with phosphorus, arsenic, antimony, bismuth, moscovium.