This document discusses different types of radioactivity, including alpha particles (a), beta particles (b), and gamma rays (g). Alpha particles have a positive charge, mass of a helium atom, and ionizing power 1000 times greater than beta particles. Beta particles have a negative charge, mass of an electron, and velocity close to the speed of light. Gamma rays are electromagnetic waves with very short wavelengths, lower ionizing power than alpha or beta particles, but move at the speed of light and have high penetrating power. The document also notes the discoveries of radioactivity in uranium by Becquerel in 1896 and polonium and radium by the Curies in 1898.

1. radio activity
1: a
1.1: + ve
1.2: charge twice of the electron
1.3: e/m 4.826×10*7 C/Kg
1.4: mass equal to helium atom
1.5: ionising power 1ooo times more than a
1.6: speed order of 10*7
1.7: counting
1.7.1: scintillation ,Giegr
2: b
2.1: -ve, mass equal to electron
2.2: similar to cathode rays
2.3: very high velocity,sometime slightly less than velocity of light
2.4: range 20 times ore than a
3: Henry Becquerral 1896 uranium
4: Madem curie and piere Curie 1898 polinium,radium
5: g
5.1: elctromagnetic wave very small wavelength,smaller than X rays
5.2: low ionising power
5.3: move with velocity light
5.4: high pentrating power