Definitions [14]
Define the term radioactivity.
The phenomenon of spontaneous disintegration of an unstable nucleus of a naturally occurring isotope accompanied by emission of active radiations, α particles, β particles and γ radiations is called radioactivity.
Define free electrons.
Electrons in outer orbits are weakly bound with the nucleus. In solids these weakly bound electrons leave their individual atom and become a part of it. These electrons are known as free electrons.
Define bound electrons.
As nucleus is positively charged it strongly attracts the negative charged electrons. The electron orbit close to the nucleus are tightly bound by strong attractive force of nucleus. These electrons are known as bound electrons.
Radioactivity is a nuclear phenomenon. It is the process of spontaneous emission of α or β and γ radiations from the nucleus of atoms during their decay.
Define half-life period.
The half-life of a reaction is the time it takes for a reactant’s concentration to decrease to half of its initial value.
The phenomenon of emission of a nucleus of helium (2He4) from a radioactive nucleus is called α-Decay.
The spontaneous emission of an electron (β⁻-decay) or a positron (β⁺-decay) from a radioactive nucleus is called β-Decay.
When a nucleus in an excited state spontaneously decays to its ground state and a photon is emitted with energy equal to the difference in the two energy levels of the nucleus, this is called γ-Decay.
The difference in the energy equivalent of the mass of the parent atom and that of the sum of masses of the products is called the Q-Value of the decay.
The time in which half the substance (radioactive) is disintegrated is called the Half-Life Period of a radioactive substance.
The nuclear phenomenon in which an unstable nucleus undergoes decay with the emission of some particles (α, β) and electromagnetic radiation (γ-rays) is called Radioactive Decay.
The rate of decay, i.e., the number of decays per unit time \[\left(-\frac{dN(t)}{dt}\right)\], is called Activity A(t).
The arithmetic average of the lives of all the nuclei present initially is called the Average Life of a radioactive element.
A nuclear reaction is a process in which atoms collide with other atoms and lose some of their original mass.
Formulae [7]
Q = [Mparent − Mproducts]c2
Q = [mX − mY − mHe]c2
Q = [mX − mY − me]c2
V ∝ A
\[E=mc^2\]
\[\rho=\frac{3m}{4\pi R_0^3}\] (constant for all nuclei)
R = R0A1/3
Key Points
- A nuclear reaction involves atoms colliding with other atoms and losing some of their original mass.
- Lost mass is converted into energy as per \[E=mc^2\].
- The two types of nuclear reactions used to produce energy are fission and fusion.
