Inspired by Röntgen's X-rays, Becquerel wanted to see if X-rays were emitted in the form of fluorescence.
He discovered that uranium salt emitted mysterious rays to darken his photographic plates.
Becquerel is a unit meaning one disintegration per second (1 Bq = 1 dps)
Alpha, a, rays are high-energy helium ions
Beta, b, rays are high-energy electrons
Gamma, g, rays are high-energy photons
The Rutherford atom: All positive charges and almost all the mass of an atom are concentrated in an atomic nucleus. The nucleus radius is only 1/100,000th of atomic radius.
Bohr assumed a planetary model for the H atom, and proposed that the angular momentum of the electrons around the nucleus is a multiple of (h/2p).
He derived the energy level for the electron,
|En = -||Z2|
|(= 4.3598e-18 J = 27.199 eV)|
Matter and energy are equivalent, suggested Einstein.
Particle and wave are dual properties for matter, theorized de Broglie who derived the equation:
|(or||l m v = h)|
Particles also have wave properties.
Electron- and neutron-diffractions confirm the theory.