What is a neutron?
A: The neutron is a subatomic particle, symbol n or n0, which has a neutral
(not positive or negative) charge, and a mass slightly greater than that of
a proton.
Protons and neutrons constitute the nuclei of what?
A: Atoms.
Since protons and neutrons behave similarly within the
nucleus, and each has a mass of approximately one atomic mass unit, they are
both referred to as what?
A: Nucleons.
Their properties and interactions are described by
what?
A: Nuclear physics.
Protons and neutrons are not elementary particles; each
is composed of what?
A: Three quarks.
The chemical properties of an atom are mostly
determined by what?
A: The configuration of electrons that orbit the atom's heavy nucleus.
The electron configuration is determined by the charge
of the nucleus, which is determined by what?
A: The number of protons, or atomic number.
The number of neutrons is what?
A: The neutron number.
Neutrons do not affect the electron configuration, but
the sum of atomic and neutron numbers is what?
A: The mass of the nucleus.
Atoms of a chemical element that differ only in neutron
number are called what?
A: Isotopes.
Some elements occur in nature with only one stable
isotope, such as what?
A: Fluorine.
Other elements occur with many stable isotopes, such as
tin with what?
A: Ten stable isotopes, and some elements such as technetium have no stable
isotope.
The properties of an atomic nucleus depend on what?
A: Both atomic and neutron numbers.
With their positive charge, the protons within the
nucleus are repelled by what?
A: The long-range electromagnetic force.
The much stronger, but short-range, nuclear force does
what?
A: Binds the nucleons closely together.
Neutrons are required for the stability of nuclei, with
the exception of what?
A: The single-proton hydrogen nucleus.
Neutrons are produced copiously in what?
A: Nuclear fission and fusion.
They are a primary contributor to the nucleosynthesis
of chemical elements within stars through what?
A: Fission, fusion, and neutron capture processes.
The neutron is essential to the production of what?
A: Nuclear power.
In the decade after the neutron was discovered by James
Chadwick in 1932, neutrons were used to induce what?
A: Many different types of nuclear transmutations.
With the discovery of nuclear fission in
1938, it was
quickly realized that, if a fission event produced neutrons, each of these
neutrons might cause what?
A: Further fission events, in a cascade known as a nuclear chain reaction.
These events and findings led to the first what?
A: The first self-sustaining nuclear reactor (Chicago Pile-1, 1942) and the
first nuclear weapon (Trinity, 1945).
Dedicated neutron sources like neutron generators,
research reactors and spallation sources produce free neutrons for use what?
A In irradiation and in neutron scattering experiments.
A free neutron spontaneously decays to what?
A: A proton, an electron, and an antineutrino, with a mean lifetime of about
15 minutes.
Free neutrons do not directly ionize atoms, but they do
indirectly cause what?
A: Ionizing radiation, so they can be a biological hazard, depending on
dose.
A small natural "neutron background" flux of free
neutrons exists on Earth, caused by what?
A: Cosmic ray showers, and by the natural radioactivity of spontaneously
fissionable elements in the Earth's crust.