Chemistry terms: N

N

n + 1 ruleHL only · also n+1 rule

A signal from hydrogen atoms with $n$ hydrogen atoms on the adjacent carbon atom(s) is split into $n + 1$ lines.

Introduced in S3.2 Functional groups: classification of organic compounds

Natural gas

A gaseous fossil fuel consisting mostly of methane, with small amounts of other alkanes, carbon dioxide and nitrogen.

Introduced in R1.3 Energy from fuels

Natural polymeralso natural polymers

A polymer made by living organisms, such as starch, cellulose, proteins, DNA and natural rubber.

Introduced in S2.4 From models to materials

neutralizationalso neutralisation, neutralization reaction, neutralize, neutralizes, neutralized

The reaction of an acid with a base to form a salt and, usually, water; for strong acids and bases in water the ionic equation is ${{\mathrm{H}{\vphantom{X}}^{+}\mskip2mu (\mathrm{aq}) {}+{} \mathrm{OH}{\vphantom{X}}^{-}\mskip2mu (\mathrm{aq})\xrightarrow{}\mathrm{H}{\vphantom{X}}_{\smash[t]{2}}\mathrm{O}\mskip2mu (\mathrm{l})}}$

neutronalso neutrons

An uncharged subatomic particle in the nucleus with a relative mass of 1.

Introduced in S1.2 The nuclear atom

Nitrating mixtureHL only · also nitration mixture, nitration, mixed acid

A mixture of concentrated nitric acid and concentrated sulfuric acid, which generates the nitronium ion and is used to nitrate benzene below about 50 °C.

Introduced in R3.4 Electron-pair sharing reactions

Nitronium ionHL only · also nitryl cation, NO2+

The linear cation ${{\mathrm{NO}{\vphantom{X}}_{\smash[t]{2}}{\vphantom{X}}^{+}}}$ (O=N⁺=O), the electrophile in the nitration of benzene, formed from concentrated nitric and sulfuric acids.

Introduced in R3.4 Electron-pair sharing reactions

Noble gasalso noble gases, group 18 elements

An element of group 18 (helium, neon, argon, krypton, xenon, radon): a very unreactive, monatomic gas with a full outer main energy level.

Introduced in S3.1 The periodic table: classification of elements

Noble gas configurationalso noble gas configurations, noble gas electron configuration

An electron configuration the same as that of a noble gas, with a full outer level (eight electrons, or two for the helium arrangement); main-group ions usually have one.

Introduced in S2.1 The ionic model

Non-directional bondingalso non-directional

Bonding in which the attraction acts equally in all directions, as in ionic and metallic bonding, so each particle is not bonded to particular neighbours.

Introduced in S2.3 The metallic model

non-polar moleculealso non-polar molecules, nonpolar molecule

A molecule with no net dipole moment, because its bonds are non-polar or its bond dipoles cancel by symmetry, such as ${{\mathrm{CO}{\vphantom{X}}_{\smash[t]{2}}}}$ and ${{\mathrm{CCl}{\vphantom{X}}_{\smash[t]{4}}}}$

Non-renewable energy sourcealso non-renewable, non-renewable energy

A finite energy source that forms far more slowly than it is used, or not at all, such as coal, crude oil, natural gas and nuclear fuels.

Introduced in R1.3 Energy from fuels

nuclear chargealso charge of the nucleus

The total positive charge of the nucleus, equal to the number of protons; a greater nuclear charge attracts the electrons more strongly.

Introduced in S1.3 Electron configurations

nuclear magnetic resonanceHL only · also NMR, magnetic resonance

The absorption of radio-frequency radiation by nuclei such as $^{1}\text{H}$ in a strong magnetic field, which flips the nuclear spin from the lower-energy to the higher-energy orientation.

Introduced in S3.2 Functional groups: classification of organic compounds

nuclear modelalso Rutherford model, nuclear atom

The model of the atom as a tiny, dense, positively charged nucleus containing almost all the mass, with electrons occupying the much larger space around it; proposed by Rutherford in 1911 from alpha-particle scattering.

Introduced in S1.2 The nuclear atom

nuclear symbolalso nuclear notation, nuclide notation, isotope notation

The notation $^{A}_{Z}\text{X}$ for an atom or ion, with the mass number at the top left, the atomic number at the bottom left and any charge at the top right.

Introduced in S1.2 The nuclear atom

nucleonalso nucleons

A particle in the nucleus: a proton or a neutron.

Introduced in S1.2 The nuclear atom

nucleophilealso nucleophiles, nucleophilic

A reactant that forms a bond to its reaction partner (the electrophile) by donating both bonding electrons; it has a lone pair and may be neutral, such as ${{\mathrm{H}{\vphantom{X}}_{\smash[t]{2}}\mathrm{O}}}$ and ${{\mathrm{NH}{\vphantom{X}}_{\smash[t]{3}}}}$

nucleophilic substitutionalso nucleophilic substitution reaction

A reaction in which a nucleophile donates an electron pair to form a new bond to an atom (usually a δ+ carbon) while another bond to that atom breaks and releases a leaving group, as in ${{\mathrm{CH}{\vphantom{X}}_{\smash[t]{3}}\mathrm{CH}{\vphantom{X}}_{\smash[t]{2}}\mathrm{Br} {}+{} \mathrm{OH}{\vphantom{X}}^{-}\xrightarrow{}\mathrm{CH}{\vphantom{X}}_{\smash[t]{3}}\mathrm{CH}{\vphantom{X}}_{\smash[t]{2}}\mathrm{OH} {}+{} \mathrm{Br}{\vphantom{X}}^{-}}}$

nucleusalso nuclei, atomic nucleus

The very small, dense, positively charged centre of an atom, containing its protons and neutrons and almost all of its mass.

Introduced in S1.2 The nuclear atom