2.1.1 State the position of protons, neutrons, and electrons in the atom.

John Dalton

• all matter is composed of tiny invisible particles called atoms
• atoms cannot be created or destroyed
• atoms in the same element are alike in every way
• atoms combine to form molecules

J.J Thompson

• different metals produce a stream of negatively charged particles, when a high voltage is applied across two electrons 
• atoms have no net charge
• 'plum pudding' model- negatively charged electrons scattered in a positively charged sponge (which is the substance)

Rutherford

• fired alpha particles at a piece of gold foil
• they would pass through which shows that the atom is mostly empty space
• large deflections occur when the positively charged alpha particles collide with and are repelled by a positively charged nucleus
• only a small number of alpha particles bounce back which means that the nucleus is very small

Bohr Model of the Hydrogen Atom

• small 'solar system' with electrons moving in orbit around the positively charged nucleus of one proton
• the electrons static forces of attraction between the oppositely charged sub-atomic particles prevents the electron from leaving the atom

Neutrons are crucial for the stability of the nuclei of later elements. Without them, positively charged protons would mutually  repel each other and the nucleus would fall apart.