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1.

Dm= [Zm_{P}+ (A - Z) m_{n}] - M OR Dm= [Zm_{H}+ (A - Z) m_{n}] - M where, Dm= Mass defect in amu m_{P}= Mass of proton in amu m_{n}= Mass of neutron in amu m_{H}= Mass of hydrogen atom A = Atomic number (number of protons) Z = Atomic mass number (number of protons and neutrons) M = Actual mass of the nucleus

2.

B.E. = 931 × Dm MeV where, B.E. = Binding energy Dm = Mass defect in amu

3.

B.E. per nucleon =

where, B.E. = Binding energy A = Atomic mass number

4.

l =

log

where, l= Decay constant in time ^{-1} t = Time for the decay N_{o}= Total number of radioactive atoms initially present (t= 0) N_{t}= Total number of radioactive atoms present at time t.

5.

t_{1/2}=

where, t_{1/2}= Half life period of the element l = Decay constant

6.

Atomic no. (Z) = Number of protons = Number of electrons

7.

Atomic mass number (A) = Atomic number (Z) + Neutron number (N)

8.

Some Important Conversions

i. 1 amu = 1.658 × 10^{-24}g = 1.658 × 10^{-27} kg

ii. 1 MeV = 10^{6} eV = 1.603 × 10^{-13} J

iii. 1eV = 1.603 × 10^{-19} J