Chemistry - Historical models of the atom

Chemistry - Historical models of the atom
As scientists discovered new evidence, the scientific model of the atom was updated or replaced.

1)An early model
Atoms were originally thought to be tiny spheres that could not be made smaller.

2 Plum pudding model
Electrons were discovered.
negative electron
The atom is a positively charged sphere containing electrons.
The alpha particle-scattering experiment showed that most positive alpha
particles fired at an atom went through the atom.

3)
Nuclear model
Atom’s mass is mainly a positive central nucleus

4)
Niel Bohr’s model
Bohr's calculations agreed with experiments showing the electron orbits.
small, positively charged sphere

experiment showed that the positive nucleus was made of small, positively charged particles, which were given the name 'protons'.

5)
Atomic model with protons

6)
Atomic model with neutrons
James Chadwick's experiments showed, about 20 years after the nucleus had been accepted, that the nucleus also contained particles with no charge; these were given the name neutron