NA number – An NA number or DOT number is a North America number assigned by the United States Department of Transportation to identify a hazardous or flammable chemical. It is analogous to a UN Number, except some chemicals have an NA number, yet don’t have a UN number. These additional NA numbers have the range NA8000 – NA9999.

nano – Nano is the prefix associated with x10^-9 and is denoted by the symbol n.
Example: Visible light has a range of wavelengths from 400 (red) to 700 (violet) nanometers.

nanometer – A nanometer is a unit of length equal to 1/1,000,000,000th of a meter. The symbol for millimeter is nm.
1 mm = 10^-9 m.

nanotechnology – Nanotechnology is the study and development of materials and objects on the nanometer level of measurement. Nanotechnology typically involves materials on the atomic or molecular level. Quantum mechanical effects play a large role in the study of nanotechnology.

naphtha – Naphtha refers to a mixture of hydrocarbons forming a flammable liquid. Naphtha is typically produced from the distillation of petroleum or coal tar. The mixture depends on the hydrocarbons used and the temperature they are boiled.
Full range naphtha consists of 5- to 12-carbon hydrocarbons boiled between 30 °C and 200 °C.
Light naphtha consists of 5- to 6-carbon hydrocarbons boiled between 30 °C and 60 °C.
Heavy naphtha consists of 6- to 12-carbon hydrocarbons boiled between 90 °C and 200 °C.
Common misspelling: naptha

naphthenes – Naphthenes are a class of cyclic aliphatic hydrocarbons obtained from petroleum. Naphthenes have the general formula C_nH_2n.
Alternate Spellings: naphthene
Common Misspellings: napthene, napthenes
Example: Cyclohexane is the simplest naphthene molecule

naphthalene – Naphthalene is an organic molecule with chemical formula C₁₀H₈ and is made of two benzene rings fused together. Naphthalene is the simplest polynuclear aromatic hydrocarbon. Also known as: albocarbon, naphthaline, naphthalin, antimite, naphthalin, bicyclo[4.4.0]deca-1,3,5,7,9-pentene
Example: Mothballs are made from naphthalene.

native element – A native element is an element in its naturally occurring form. Native elements are nearly always impure samples.
Example: Copper is a native element often found in its pure, uncombined form.

natrium – Natrium is the original Latin name for the element sodium. Natrium is the source of sodium’s element symbol Na.

natural abundance – Natural abundance is the measure of the average amount of a given isotope naturally occurring on Earth.
Example: There are two natural isotopes of boron: 10B and 11B. The natural abundance is 19.9% of 10B and 80.1% of 11B.

necrosis – Necrosis is the destruction of one or more cells from an external cause such as a toxin, infection, radiation or trauma.
Example: Ultraviolet radiation can cause necrosis of the skin in the form of a sunburn.

negatron – A negatron is a negatively charged particle emitted during β- decay. Negatron is also a term used to describe any electron.
Also Known as: beta particle, electron

nematic – Nematic refers a substance where the arrangement of individual molecules is parallel to each other but not arranged in layers or rows. Nematic phase refers to liquid crystals when the crystals are aligned, but not arranged. If the individual molecules are parallel and arranged in layers or rows, the substance is said to be smectic.

neodymium – Neodymium is the name for the lanthanide element with atomic number 60 and is represented by the symbol Nd. neon – Neon is the name for the noble gas element with atomic number 10 and is represented by the symbol Ne.

nephrotoxicant – A nephrotoxicant is a toxic compound that can cause damage to the kidneys.
Example: Acetaminophen is a common over-the-counter drug that is a nephrotoxicant.

neptunium – Neptunium is the name for the actinide element with atomic number 93 and is represented by the symbol Np.

Nernst equation – The Nernst equation is an equation relating the voltage of a chemical cell to its standard cell potential and to the concentrations of the reactants and product.
The Nernst equation is:
Ecell = E0cell – (RT/nF) x log10Q
where
Ecell is the cell potential
E0cell refers to standard cell potential
R is the gas constant
T is the absolute temperature
n is the number of moles of electrons transferred by the cell’s reaction
F is Faraday’s constant
Q is the reaction quotient, where Q = [C]c·[D]d / [A]a·[B]b
where A, B, C, and D are chemical species; and a, b, c, and d are coefficients in the balanced equation:
aA + bB → cC + dD
Example: At 25 °C, the Nernst Equation can be expressed as:
Ecell = E₀cell – 0.0591/n x log10Q

net ionic equation – A net ionic equation is a chemical equation for a reaction which lists only those species participating in the reaction.
Example: The net ionic equation for the reaction that results from mixing 1 M HCl and 1 M NaOH is:
H+(aq) + OH–(aq) → H₂O(l)
The Cl– and Na+ ions do not react with anything and are not listed in the net ionic equation.

network solid – A network solid is a substance made up of an array of repeating covalently bonded atoms.
Example: Diamonds are network solids made of carbon atoms.

neurotoxicant – Neurotoxicant is a toxic compound that can cause damage to the central nervous system.
Examples: Lead, aluminum, ammonia, and benzene are all neurotoxicants

neutral solution – A neutral solution refers to an aqueous solution with a pH of 7.0 ([H+] = 1.0 x 10^-7 M).

neutralization – Neutralization is a chemical reaction between an acid and a base which produces a neutral solution (pH = 7).

neutrino – A neutrino is a fundamental particle with no electric charge and travels at speeds close to the speed of light. The symbol for neutrino is the Greek letter ν.
There are three types of neutrinos, each one associated with a partner particle.
νe electron neutrino
νμ = muon neutrino
ντ = tau neutrino
Example: Neutrinos are formed during some types of nuclear decay and when cosmic radiation collides with atoms in the atmosphere.

neutron – The neutron is the particle in the atomic nucleus with a mass = 1 and charge = 0.

neutron emission – Neutron emission is a type of radioactive decay where an atom’s nucleus ejects an energetic neutron. Neutron emission is commonly abbreviated by a lower case n.
Example: The isotope of hydrogen 4H decays by neutron emission by ejecting a 6.73 MeV neutron, forming 3H.

newton – A newton is the SI unit of force. The symbol for newton is N.
One newton is equal to the amount of force needed to accelerate a 1 kg. mass 1 m/sec².
1 N = 1 kg·m/s²

nickel – Nickel is the name for the transition metal element with atomic number 28 and is represented by the symbol Ni.

nihonium – Nihonium is the name for the basic metal element with atomic number 113 and is represented by the symbol Nh. The name nihonium replaced the old placeholder name ununtrium in 2016.

niobium – Niobium is the name for the transition metal element with atomic number 41 and is represented by the symbol Nb. Niobium is also called Columbium.

nitrate – A nitrate is an ion with the chemical formula NO^3-. Nitrates are also compounds that contain the nitrate ion.
Example: Ammonium nitrate (NH₄NO₃) is a nitrate.

nitrile – A nitrile is an organic compound containing the -C≡N functional group. The -C≡N group is called the nitrile functional group. Nitrile compounds commonly contain the prefix cyano- in their names.
Example: Hydrogen cyanide is a simple nitrile compound.

nitrite – A nitrite is an ion with the chemical formula NO^2–. Nitrites are also compounds that contain the nitrite ion.
Example: Ammonium nitrite (NH₄NO₂) is a nitrite.

nitro compound – A nitro compound is an organic compound containing the nitro functional group (-NO₂).

nitrogen – Nitrogen is the name for the nonmetal element with atomic number 7 and is represented by the symbol N. Nitrogen is also called azote.

nitrogenous base – A nitrogenous base is a heterocyclic base containing nitrogen that forms the base part of nucleotide molecules.
Also known as: nucleotide base, nucleobase
Examples: Cytosine, guanine, and adenine are all nucleotide bases.

nitro group – Nitro group is a functional group containing nitrogen and oxygen in the form -NO₂.

nobelium – Nobelium is the name for the actinide element with atomic number 102 and is represented by the symbol No.

noble gas – Any of the elements found in Group 8 at the far right of the Periodic Table. Noble gases have full electron shells to the maximum number for their energy level.
Examples: Helium, argon, xenon are all noble gases.

noble gas core – A noble gas core is an abbreviation in an atom’s electron configuration where the previous noble gas’s electron configuration is replaced with the noble gas’s element symbol in brackets.
Example: Sodium has an electron configuration of 1s²2s2p⁶3s¹.
The previous noble gas on the periodic table is neon with an electron configuration of 1s²2s²2p⁶. If this configuration is replaced by [Ne] in sodium’s electron configuration it becomes [Ne]3s¹. This is the noble gas core notation of sodium.

nonbonding electron – A nonbonding electron is an electron in an atom that does not participate in bonding with other atoms.
Example: The 1s orbital electrons of a lithium atom are nonbonding electrons. Bonds are formed with the 2s electron.

nonelectrolyte – A substance that does not exist in an ionic form in aqueous solution.
Example: Ethyl alcohol (ethanol) is a nonelectrolyte because it does not ionize when dissolved in water.

nonflammable – Nonflammable is the property of a material rendering incapable of being burned. Antonym: flammable, inflammable

nonmetal – One of the elements which do not exhibit metallic properties, generally located in the upper righthand corner of the Periodic Table.
Examples: Oxygen and nitrogen are both nonmetals.

nonoxidizing acid – A nonoxidizing acid is an acid that cannot act as an oxidizing agent.
Examples: Hydrochloric acid, hydroiodic acid, hydrobromic acid, hydrofluoric acid, phosphoric acid are all nonoxidizing acids.

nonpolar bond – Type of chemical bond which has no positive or negative ‘ends’.
Examples: Nonpolar bonds are found in diatomic and homonuclear molecules, such as O2 and N2.

nonpolar molecule – Molecule which has no separation of charge, so no positive or negative poles are formed.
Examples: O₂, CO₂, N₂ are all nonpolar molecules.

nonspontaneous reaction – A reaction which cannot occur without the input of work from an external source. ΔG > 0 for nonspontaneous reactions at a set temperature and pressure.

nonvolatile – Nonvolatile refers to a substance that does not readily evaporate into a gas under existing conditions.
Example: Glycerin (C₃H₈O₃) is a nonvolatile liquid.

normal – There are two meanings for ‘normal’ in chemistry.

1. Normal or normal concentration refers to a concentration of solutes that is the same in two samples.
2. Normality is the gram equivalent weight of a solution in a solution, which is its molar concentration divided by an equivalence factor. It is used in situations where molarity or molality might be confusing or else difficult to determine. Also known as: normality, N, isotonic
   Examples: (Definition 1) A 9% salt solution has a normal concentration with respect to most human body fluids.
   (Definition 2) A 1 M sulfuric acid (H₂SO₄) is 2 N for acid-base reactions because each mole of sulfuric acid provides 2 moles of H+ ions. A 2 N solution is called a 2 normal solution.

normal boiling point – Normal boiling point is the temperature at which a liquid boils at 1 atmosphere of pressure.

normal concentration – See normal definition above.

normality – Normality is a measure of concentration equal to the gram equivalent weight per liter of solution. Gram equivalent weight is the measure of the reactive capacity of a molecule. The solution’s role in the reaction determines the solution’s normality.
For acid reactions, a 1 M H₂SO₄ solution will have a normality (N) of 2 N because 2 moles of H+ ions are present per liter of solution.
For sulfide precipitation reactions, where the SO₄^- ion is the important part, the same 1 M H₂SO₄ solution will have a normality of 1 N.

normal melting point – Normal melting point is the temperature at which a solid melts at 1 atmosphere of pressure.

nuclear binding energy – Nuclear binding energy is the amount of energy required to hold an atom’s protons and neutrons together in the nucleus.

nuclear fission – Nuclear fission is the process where a heavy atomic nucleus is split into two or more smaller nuclei and energy is released.

nuclear fusion – Nuclear fusion is the process where two atomic nuclei are combined to form a single larger atomic nucleus and energy is released.

nuclear radiation – Nuclear radiation refers to the particles and photons emitted during reactions that involve the nucleus of an atom.
Example: During the fission of U-235 the nuclear radiation that is released contains neutrons and gamma ray photons.

nuclear shell model – The nuclear shell model is a model of the nucleus of an atom where the protons and neutrons are arranged according to energy levels or shells. The nuclear shell model helps explain the stability of the nucleus as more nucleons are added.

nucleation – Nucleation is the process where droplets of liquid can condense from a vapor, or bubbles of gas can form in a boiling liquid. Nucleation can also occur in crystal solution to grow new crystals.
Examples: Dust and pollutants provide nucleation sites for water vapor in the atmosphere to form clouds. Seed crystals provide nucleation sites for crystal growing.

nucleic acid – Nucleic acids are biological polymers made from nucleotide monomers.
Example: DNA and RNA are nucleic acids.

nucleobase – A nucleobase is a heterocyclic base containing nitrogen that forms the base part of nucleotide molecules.
Also known as: nucleotide base, nitrogenous base
Examples: Cytosine, guanine, and adenine are all nucleotide bases.

nucleon – Nucleon is another name for the particles that make up an atomic nucleus: protons and neutrons.

nucleophile – A nucleophile is an atom or molecule that donates an electron pair to make a covalent bond.
Also known as: Lewis base
Example: OH– is a nucleophile. It can donate a pair of electrons to the Lewis acid H+ to form H₂O.

nucleophilic addition – Nucleophilic addition is an addition reaction where a nucleophile donates an electron pair to an electron deficient atom to form a new molecule.

nucleoside – A nucleoside is a compound formed from a nucleotide base and a five-carbon sugar.
Examples: Cytidine, uridine, adenosine and guanosine are all nucleosides.

nucleosynthesis – Nucleosynthesis is the formation of new atoms heavier from hydrogen in the interior of stars and from other processes.

nucleotide – A nucleotide is an organic molecule made up of a nucleotide base, a five-carbon sugar (ribose or deoxyribose) and at least one phosphate group. Nucleotides make up the basic units of DNA and RNA molecules.

nucleotide base – Another word for nucleobase. See definition above.

nucleus – Nucleus means center. In chemistry, nucleus refers to the positively charged center of the atom containing protons and neutrons.

nuclide – Nuclides are an atom or ion characterized by the contents of their nucleus.
Examples: 12C₆ and 14C₆ are both nuclides.

null hypothesis – The null hypothesis is the proposition that implies no effect or no relationship between phenomena. The null hypothesis is popular because it can be tested and found to be false, which then implies there is a relationship between the observed data.
Also Known as: H0, no-difference hypothesis
Example: “Hyperactivity is unrelated to eating sugar.” is an example of a null hypothesis. If the hypothesis is tested and found to be false, using statistics, then a connection between hyperactivity and sugar ingestion may be indicated.

nurse tank – A nurse tank is a container used exclusively to transport anhydrous ammonia.

nutraceutical – Nutraceutical is any substance that is a food or a part of a food and provides medical or health benefits, including the prevention and treatment of disease. Nutraceutical products may range from isolated nutrients, dietary supplements and specific diets to genetically engineered designer foods, herbal products, and processed foods such as cereals, soups, and beverages.
Example: beta-carotene, lycopene