Nuclear Energy

nucleus is called radioactivity, and the nucleus is said to have undergone radioactive decay, or just
decay. In this process, the nucleus changes its composition and may actually become a different
nucleus entirely. The process continues till the nucleus achieves stability.
For example, most carbon (Z = 6, A lx =12) atoms are stable, with the nucleus having six
protons and six neutrons. Carbon has an isotope, C-14, whose nucleus consists of six protons and
eight neutrons, which is unstable. In its attempt to achieve stability, a C-14 nucleus gives off a beta
particle (that is, an electron emitted by an atomic nucleus). After the C-14 nucleus has lost the beta
particle, it now consists of seven protons and seven neutrons. But a nucleus consisting of seven
protons and seven neutrons is no longer a carbon nucleus. It is now the nucleus of a nitrogen atom.
By giving off a beta particle, the C-14 atom has changed into a N-14 atom.
In the periodic table, elements with atomic number 83 and above are unstable, meaning all
their isotopes emit radioactivity. lxi Elements with atomic number from 1 to 82 are mostly stable
[with the exceptions of technetium (Z=43) and promethium (Z=61)], but some have unstable
isotopes.
Types of radiation emitted by radioactive elements
Radioactive isotopes spontaneously emit several types of radiation in the form of photons or
high-energy particles while transforming to a stable isotope, of which three are the most common:
i. Alpha radiation: Alpha particles are composed of two protons and two neutrons. Being
heavy (as compared to beta particles), these particles do not travel very far, and are not able to
penetrate dead cells in the skin to damage the underlying living cells. Therefore, when outside
the human body, alpha particles are not dangerous to human life. However, when alpha particles
are inhaled into the lungs or ingested into the gastrointestinal tract, they come into contact with
living cells and severely damage them. The biological damage can have serious consequences
for human health, including the possibility of causing cancer. For instance, Plutonium is an
alpha emitter, and no quantity inhaled has been found to be too small to induce lung cancer in
animals.
ii. Beta radiation: This is composed of electrons. Beta particles are lighter than alpha particles
– like a bullet compared to a cannon ball – and so while they travel farther than alpha in body
tissues, the biological damage caused by them is less. They can penetrate the outer layer of dead
skin and damage the underlying living cells. If they are inhaled or consumed or absorbed into
the blood stream, then they can damage the tissues and cause cancer. Typically, how beta
emitters act is by accumulating in the human body, causing low level exposure over a prolonged
period of time, and the main health effect of this prolonged exposure is cancer. Usually, health
effects of beta particles develop relatively slowly, typically over 5-30 years. For instance,
Iodine-131 concentrates heavily in the thyroid gland, increasing the risk of thyroid cancer and
other disorders (How does a nucleus emit a electron? The answer: a neutron breaks up into a
proton and electron, and the latter is emitted.)
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