Radioactivity – discovered by Henry Becquerel.

“  spontaneous emission of active radiation from a radioactive substance called radioactivity .Those elements emitting such radiations called radioactive elements.

3 types of radiations are emitted:

1. α-rays – 1. Deflected towards negative plate

2. having positive charge called X-rays

                The particle present in them called X-particle. Each X-particle has chage+2 unit +mass unit (He₂⁴)

2. β- rays- 1. Deflected towards positive plate

2. Having negative charge called β-rays

                The particle present in them called β-particle.

                β-particle possess same charge + mass as electron (_-1 ^oe)

3. γ-rays- 1.They remains un-deflected

2.They are simple electromagnetic radioactive (ϒ^o_o)