N

N

atomic symbol for nitrogen

Na

atomic symbol for sodium

Nb

atomic symbol for niobium

NBS

abbreviation for the National Bureau of Standards (see NIST)

Nd

atomic symbol for neodymium

Ne

atomic symbol for neon

negatron

(negatively charged) electron, so designated to distinguish it clearly from its antiparticle, the positively charged positron

Note: The term negatron is widely considered to be obsolete.

net

after subtraction of background, tare, or other corrections (as in net count rate) — cf. gross

net count

gross count after correction for the background or blank signal and any other interferences

net count rate

gross count rate after correction for the background or blank signal and any other interferences

net mass

total mass of material and container (or measured gross mass) minus the mass of the container (or measured tare mass)

neutron activation

activation (inducement of radioactivity) by neutron bombardment

neutron activation analysis

activation analysis involving neutron activation

neutron number (N)

number of neutrons in an atomic nucleus

Ni

atomic symbol for nickel

NIST

National Institute of Standards and Technology, formerly the National Bureau of Standards (NBS), which is the national metrology institute for the United States and a member organization of the International Organization for Standardization (ISO)

No

atomic symbol for nobelium

NORM

naturally occurring radioactive material

normal distribution

A random variable, X, has the normal distribution with parameters μ and σ² (the mean and variance, respectively) if it has the probability density function:

f(x) =

1 σ√ 2π

exp

(

−

(x − μ)2 2σ2

)

A normal distribution is also called a Gaussian distribution.

Np

atomic symbol for neptunium

nuclear counting

See radiation counting

nuclear decay

spontaneous nuclear transformation [IUPAC]

(nuclear) disintegration

a nuclear decay

Note: Use of the term disintegration to mean nuclear decay is well established; how­ever, it may be a mis­nomer for certain types of decay, such as electron capture, where the nucleus does not “disintegrate” in the usual sense of the word.

nuclear instrumentation

generally, instrumentation used for radia­tion count­ing measurements

nuclear fission

splitting of an atomic nucleus

nuclear fusion

joining of two atomic nuclei to form a new nucleus

nuclear isobars

nuclides having the same mass number but different atomic numbers

nuclear isomers

nuclides having the same mass number and atomic number, but occupying different nuclear energy states [IUPAC]

Nuclear Regulatory Commission (NRC)

federal regulatory agency responsible for licensing and inspecting nuclear power plants and other facilities using radioactive materials

nuclear transformation

change of one nuclide into another

nuclear transition

change of a nucleus from one state to another

nucleide

French spelling of nuclide

nucleon

proton or neutron

nucleon number (A)

total number of protons and neutrons (i.e., nucleons) in an atomic nucleus — also called mass number

nucleotide

one of the chemical building blocks of DNA or RNA (cf. nuclide)

A nucleotide consists of a nitrogenous base (adenine, guanine, thymine, or cytosine in DNA; adenine, guanine, uracil, or cytosine in RNA), a sugar molecule (deoxyribose in DNA; ribose in RNA), and a phosphate group.

nuclide

species of atom, characterized by its mass number, atomic number and nuclear energy state, provided that the mean life is long enough to be observable [IUPAC] (cf. nucleotide)

nuclidic mass

rest mass of a nuclide expressed in atomic mass units [IUPAC]

null hypothesis (H₀)

in a statistical hypothesis test, the hypothesis that is presumed to be true unless the data provide sufficient evidence to the contrary (cf. alternative hypothesis)

numerical value (of a quantity)

value of a quantity divided by the unit of measurement in which it is expressed

The numerical value of a quantity is simply a number.