the atomic structure: historical development of atomic models

HISTORICAL DEVELPOMENT OF ATOMIC MODELS

John Dalton (1766-1844)
**All element are made up of tiny
indivisible particles called atom
**atoms cannot be create
or destroyed
**the atom of element are alike,
but differ from atoms of
another element.
**all chemical reactions results
from the combination or
separation of atom.

James Chadwick (1891-1974)
**discover the existence of
neutrons in the nucleus
**The neutron is neutral
**The neutrons has a mass almost
the same as that of a proton

Ernest Rutherford (1871-1937)
**Discovered proton
**he conclude that almost the
entire mass of the atom
is contained in a small volume
called nucleus
**the nucleus contain positively
charged particles called proton
**most part of the atom contained
empty spaces.

Neils Bohr (1885-1962)
** proposed that the electrons
in an atom move around the
nucleus in fixed shell

J.J. Thompson (1856-1940)
**discovered negatively
charged particles called
electrons
**described the atom as
sphere of positive charge
with electrons scattered
around in the sphere