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?
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?
Their properties and interactions are described by
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?
Some elements occur in nature with only one stable
isotope, such as what?
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
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.