Radioative Decay

Types of Radioactive Decay
The type of radioactive decay that occurs usually depends on whether the nucleus is above or below or to the right of the stability belt.There are five common types of radioactive decay.
1.Alpha Emission
2.Beta Emission
3.Positron Emission
4.Electron Capture
5.Gamma Emission
Half-life period
The time required for half of a radioactive substance to disintegrate is known as the half-life period, represented here by t1/2
Radioactive Isotopes and Isobars
A radioactive isotope is formed by the emission of one alpha and bita paricles, while an isobar is formed by the emission of one bita particle.
Binding Energy of the Nucleus
It has been observed that the actual mass of an isotope of an element, obtained experimentally using mass spectrograph, is invariably less than the calculated mass of the isotope. This mass difference is known as mass defect of the nucleus which is also expressed as the packing fraction of the nucleus.
Packing fraction = isotopic mass - mass number/mass number x 10000

Neutron-Proton Ratio and Nuclear Stability

Most naturally occurring nuclides hav even numbers of neutrons and even numbers of protons. Nuclides with odd numbers of both neutrons and protons are least common and those with odd-even combinations are intermediate in abundance.
No. of protons even even odd odd
No. of neutrons even even even odd
No. of stable nuclides 157 52 50 5
A plot of the number of neutrons versus the number of protons shws that as the atomic number increases, the N/P ratio of the stable nuclides increases.

Quantum Numbers and Electronic Configuration

The following rules help us to predict electronic configuration
of atoms with the help of quantum numbers
1. Electrons are added into orbitals in the way that gives the
lowest total energy for the atom.
2. Electrons are assigned to orbitals in order of increasing
value of (n+l).
3. For subshells with the same value of (n+l), electrons are
assigned first to the subshell with lower n.
4. No two electrons in an atom may have identical sets of four
quantum numbers.
5. Electrons occupy all the orbitals of a given subshell singly
before pairing begins. These unpaired electrons have parallel
spins. (Hund Rule). Hund rule states that for degenerate
orbitals, the lowest energy is attained when the number of
electrons with the same spin is maximized.