Physics [2 Mark Question Answer]

Ionisation power of a particle is maximum. It is about 100 times more than that of β particles. Ionisation power of β particle is about 100 times more than that of γ radiations. γ radiations have least ionisation power.

The penetrating power of α particle is least. Penetrating power of β
particles is less but 100 times more than that of a particle. γ radiations have
maximum penetration power. They are 100 times more penetrating than β
particles.

Atomic number is the number of protons present in the nucleus. As number of protons is equal to the number of electrons so atomic number also gives the number of electrons in an atom.

Atom consists of three elementary particles, neutrons, protons and electrons. Neutron and protons form the central part of atom called nucleus where electrons revolve around this central part in orbits called electronic orbits.

Radioactivity is the spontaneous random emission of particles from within the nucleus of atom. Radiations are emitted from nucleus of atom thus radioactivity is a nuclear phenomenon. 

(i) β particles are negatively charged particles with negIigible mass so when a element emits a β particle its mass remain same but atomic number decreases by 1 unit. So after emitting a β particle position of element would shift 1 unit left to the periodic table in same row.
(ii) Y radiations a re uncharged and have no mass. So there is no change in atomic mass and atomic number of element emitting Y radiations and position of element remain same in pe rio die table.

Radioactive substances should not be touched by hands because radiation emitted by radioactive substances can cause burns, Leukaemia, eye cataract, sterility or many other dangerous disease. 

Atomic number is the number of protons present in the nucleus. As number of protons is equal to the number of electrons so atomic number also gives the number of electrons in an atom.