he believe that all matter consisted of extremely small particles that couldn't be divided.
He believed in five elements : earth, air, fire, water, and aether.
All matter is made of atoms Atoms are indivisible and indestructible
Max Planck developed the concept of quantum mechanics.
suggested a model of the atom as a sphere of positive matter in which electrons are positioned by electrostatic forces
atomic theory in which the atom has a positive nucleus by surrounded negative electrons.
He completed his theory of atomic structure.
all atoms and molecule His work led to the atomic cloud model
He discovered the mass of electron and it was zero
Werner Heisneberg discovered the Heisenberg Uncertainty Principle
His ideas were a basis for developing the wave mechanics theory
He discovered the neutron.