Radioactivity is the means by
which the nucleus of an unstable atom loses energy (decay) by releasing radiation.
It is also known as nuclear decay. Before I delve into the subject of
radioactivity proper I should give you the background and context to
radioactivity.
The universe is all time and space
and its contents. It includes planets, stars and galaxies, contents of
intergalactic space, atomic particles, all matter and energy. Broadly speaking
the universe contains dark energy, ordinary energy, dark matter, ordinary
matter, electromagnetic radiation and antimatter. Electromagnetic radiation are
visible light (sunlight), radio waves, infrared light and X-ray. The universe
is defined to cover everything that has existed in the past, is existing now, and
yet to exist in the future, as it expands. The size of the universe is not
known but part of it is observable.
The next logical subject I should
like to consider as I proceed is matter, a content of the universe. There are
two types of matter. One is dark matter and the other is ordinary matter. Matter
is the substance of which material things are made.
Dark matter is not seen but it is
determined by the gravitational effect it has on visible matter, radiation and
the universe. Dark matter forms a larger part of the matter in the universe- 84.5%.
Dark matter does not take in or release light on a significant level.
Ordinary matter are atoms, ions, electrons
and objects they constitute. These are stars, gases between stars, gases
between galaxies, planets and objects we use in everyday life. Living organisms like plants, animals and
humans are made of matter. Ordinary matter can easily be found in four states:
solid, liquid, gas and plasma.
From the foregoing paragraph
there is a hint that the natural environment is made of ordinary matter. Inside
of ordinary matter are atoms. The Earth holds about 1.33× 10⁵⁰ atoms. It was
believed that there were between 10⁷⁸- 10⁸² atoms in the known observable
universe (July, 2009). Bringing it to ordinary numbers we get between ten quadrillion
vigintillion and one hundred thousand quadrillion vigintillion atoms! It is
very difficult to wrap one’s mind around such figures. Living organisms have cells and the cells are
made of molecules which are bonded atoms. Atom is the basic building block of
matter. The atom has a nucleus or its center. The nucleus consist of protons
and neutrons. There is also electrons which moves around the nucleus. The
number of protons in the atom is its atomic number. Inside of the protons and
neutrons are subatomic particles called quarks.
The following diagram attempts to
give an illustration of how matter is arranged structurally:
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MATTER
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ATOM
(smallest unit of matter)
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ELECTRONS
(It orbits the nucleus)
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PROTONS
(one half of nucleus where decay takes
place)
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NEUTRONS
(other half of nucleus where decay
takes place)
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QUARKS
(subatomic particles in protons)
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QUARKS
(subatomic particles in neutrons)
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I have stated from the beginning that
radioactivity is the decaying of the nucleus of an unstable atom. Also, I have
managed to indicate how the atom is structurally arranged within ordinary
matter. There are atoms in you as a human being. There are atoms in the wine or
whisky that you drink. How then does the decay take place? Protons and neutrons
forming the nucleus of the atom attract each other. Protons repel each other.
However neutrons attract each other. So protons attract neutrons but reject
their kind, whereas neutrons attract both protons and their own kind in the
nucleus. A balance must be struck where protons and neutrons must coexist. If
that does not happen the nucleus becomes unstable and decay may set in. Radioactivity
is spontaneous in that it is not subjected to any external factor like
temperature, pressure, electric and magnetic fields etc. When radioactivity
takes place the nucleus releases alpha particles, beta particles, gamma rays
and conversion electrons.
Radioactivity therefore results
in three main types of radiation:
ALPHA
Alpha decay is a radioactive
decay in which the nucleus of the atom emits alpha particles or helium nucleus.
Helium is the second most abundant element in the observable universe. Alpha
particles carry positive charge.
BETA
Beta decay is a radioactive decay
in which the nucleus of the atom emits electron or positron and neutrino,
leading to a proton being changed into a neutron or the other way round. A positron
is antimatter of electron. Neutrino is an elementary particle that does not
undergo strong interactions. Beta particles carry negative charge.
GAMMA
Gamma decay is the decay of the
nucleus of atom from a high energy level to lower energy level resulting in
gamma radiation. Electromagnetic radiation from decay of atomic nucleus is
gamma ray.
Atoms are either stable or
unstable. Unstable atoms undergo radioactivity. The stability status of an atom
is determined by its atomic number or the number of protons it has.
On the whole, the point I want to
make is that the natural environment, as part of the observable universe is
full of atoms- air, water and soil. Living things and everyday things we come
into contact with contain atoms too. The atoms are either stable or unstable.
The unstable atoms undergo radioactivity. Some radioactivity are man-made e.g.
Chernobyl and Japan nuclear incidents.
Reference:
http://www.universetoday.com/36302/atoms-in-the-universe/
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