12. Definitions of some nuclides:
13. Nuclear stability:
14. Soddy-Fajan group displacement law:
15. Some important mathematical relations:
A. kt = 2.3031og(N0/N);
B. t1/2 = 0.693/k;
C. tav ----- 1/k
where, N0 = no. of radioactive atoms present initially,
N = no. of radioactive atoms present after time t,
k = rate constant,
t1/2 = Half-life period and tav = Average life period.
16. There are four disintegration series.
1. Thorium series (4n),
2. Uranium series (4n+2),
3. Actinium series (4n+3) and
4. Neptunium series (4n+1).
The first three of them are naturally occurring while the last one is artificially made.