Claimed that matter could not be
divided into smaller pieces forever
John Dalton
Thought atoms are tiny solid ball,
came up with atomic theory
In 1805, John Dalton published his
atomic theory
All matter is made of tiny particles
called atoms
Atoms are tiny hard spheres that cannot
be broken down into smaller parts
Atoms cannot be
created or destroyed
Atoms in an element always
have the equal amount of
protons and elctrons
J.J Thomson
Discovered electrons and also discovered
atoms are made from positive and negative
charged electrons
Rutherford
Discovered protons and nucleus. He called
positive particles "protons" and the center
of atoms the nucleus. He showed that
atoms have positive particles in the center
and mostly empty space.
Niels Bohr
Improved on Rutherford model and
proposed that electrons move
around the track around nucleus
known as the shell.
Chadwick
Discovered particles with no
charge and called it "Neutrons".
Neutrons are also found in the
nucleus.
The new atomic model has
electrons moving around the
nucleus in a cloud.
The overall diameter of an atom can be 100,000 times
Atoms are made up of electrons
together with heavier subatomic
particle called protons, electron and
neutrons, these particles have very,
very small masses and electric charges
The actual mass of a proton is 1.67*10 g
It is impossible to know where an electron is at
any given time