Download The Dalton Thompson 1889 Rutherford Niels Bohr Moseley

‘Matter is composed of atoms’
The
Dalton
‘too small for eyes to see’
‘Different elements have
different atomic structure’
‘Atoms can combine with other
atoms to make a compound’
Thompson 1889
Discovered the electron, which are found in all atoms
‘Electrons have a negative charge’
A ‘Plum Pudding’
model of an atom
was proposed Where an atom has
free electrons,
surrounded by a sea
of positive charges
to make it neutral.
Rutherford
The famous ‘gold foil experiment’ by Rutherford proved the ‘Plum Pudding’ model wrong as
not all alpha particles passed through the gold atoms, some were deflected. The positively
charged alpha particle hit a positive substance which caused it to be deflected, therefore atoms
must have a nucleus where most of its mass is concentrated and contained neutrons and
positive charges called protons.
Niels Bohr
Moseley
Moseley who studied
under Rutherford, rearranged the previous
periodic tables and
ordered elements in
their atomic number
instead of mass.
Bohr introduced a new model of the
atomic structure and proposed the
idea of energy levels or shells where
the electrons can move and travel
around the nucleus at an orbit.