physics paper 1

John Dalton found atoms. J.J. Thomson discovered electrons and found the plum pudding model. Rutherford did the alpha scattering experiment that led to the discovery of the nucleus that was positively charged (nuclear model). Niels Bohr found electrons orbit in shells. James Chadwick proved the neutron. The number of protons = number of electrons. 

Isotopes are different forms of the same element - different number of neutrons.

Unstable isotopes tend to decay into other elements and give out radiation to become more stable - radioactive decay.

Alpha particles are high-speed electrons (two neutrons and two protons). They have low penetrating power but are strongly ionising. 

Beta particles are high-speed electrons that are moderatley ionising and penetrate moderately far into materials. 

Gamma rays are EM waves with a short wavelength from…