How many electrons are shared between the two atoms in a nitrogen (N2) molecule?

A nitrogen atom has atomic number 7, and its electronic configuration is 2, 5. It has five electrons in its outer (valence) shell and needs three more to complete an octet. In a nitrogen molecule, each of the two nitrogen atoms contributes three electrons for sharing. Together they share three pairs of electrons, that is, six electrons. This forms a triple covalent bond, written N≡N.

Each nitrogen atom is left with one lone pair of electrons that is not involved in bonding. The Lewis structure is therefore :N≡N:.

A triple bond consists of one sigma (σ) bond and two pi (π) bonds. The nitrogen-nitrogen triple bond is one of the strongest chemical bonds known, with a bond dissociation energy of about 946 kJ per mole. Because this bond is so strong, nitrogen gas is very unreactive (inert) at ordinary temperatures. This is why nitrogen is used to fill food packets (such as chip packets) to prevent spoiling, and why most living things cannot use atmospheric nitrogen directly. It must first be "fixed" into compounds, either by nitrogen-fixing bacteria such as Rhizobium in the root nodules of legumes, by lightning, or industrially by the Haber process (in which nitrogen and hydrogen combine to form ammonia over an iron catalyst).

Nitrogen makes up about 78% of the Earth's atmosphere by volume.

Bond types compared:

• Single bond: one shared pair (2 electrons), as in H2 or Cl2.
• Double bond: two shared pairs (4 electrons), as in O2.
• Triple bond: three shared pairs (6 electrons), as in N2.

Why not the other options?

• ✗Two electrons are shared in a single bond, as in H2.
• ✗Four electrons are shared in a double bond, as in O2.
• ✗Eight is incorrect; no common molecule has a quadruple bond of this kind.