Section 7: Radioactivity and particles

Is divided into three main topics

a) Units
b) Radioactivity
c) Particles

The whole section is divided into 20 subsections as 7.1-7.20

a) Units

Examiner's Expectation: 7.1  In this section Students are required to rote learn following terms and their units

S.No Term Definition Units


Number of atoms of an unstable element decaying per second.

Extra Information:

Activity always falls with time.

Becquerel (Bq)

1 Bq = 1 decay per second

2 Half-life Time taken for half of the nuclei of a sample to decay. Per second,per minute,per hour or per year
3 Time Second,minute,hour and year
4 Distance Centimeters (cm)
5 Fission or Nuclear Fission

It is a process whereby heavy unstable nuclides break up to produce energy.

Extra info:

Fission reaction is started by firing a neutron at a Uranium-235 nucleus. The extra neutron makes Uranium more unstable and splits it into fragments.

6 Fission Chain reaction
A neutron causes a Uranium-235 nucleus to split, producing more neutrons, which cause more nuclei to split and so on.
7 Radioactivity

Radioactivity is a process in which an unstable atom tries to stablize itself by emitting radiations in the form of Alpha, Beta and Gamma.

Extra info:

Radioactivity is a spontenous random process.

Radioactivity is a decay process ie the size of the atom diminishes after each emission.

You can not increase or decrease the rate of radioactivity decay by changing temperature, pressure or by chemicals.