Page 18 - ICSE Chemistry 6

John Dalton

John Dalton is credited for proposing the modern atomic theory. He also gave
the Law of MulƟ ple ProporƟ ons and the Law of ParƟ al Pressures.

Thirst for Knowledge

J.J. Thomson

J.J. Thomson discovered the electron and proposed the ‘Plum Pudding Model’,
according to which electrons are embedded in a cloud of protons. The model
represents that electrons are surrounded by posiƟ ve charges in order to
balance negaƟ ve charges. Thomson helped us to have a beƩ er understanding
of the atom and its structure.

Ernest Rutherford
Ernest Rutherford performed the famous ‘gold foil experiment’. He proposed
that protons lie at the centre of an atom in the nucleus, and are surrounded
by electrons. He also discovered the concept of radioacƟ ve half-life.

Niels Bohr
Niels Henrik David Bohr developed the ‘Bohr model of an atom’ or ‘Bohr
atomic model’. He proposed that energy levels of electrons are discrete
and electrons revolve in orbits around the nucleus of an atom.

Some Important Chemists/ScienƟ sts

Antoine Dmitri Ernest
John Dalton J.J. Thomson Niels Bohr
Lavoisier Mendeleev Rutherford

• Discovery of Modern • Discovery of • Gold foil Bohr model of
role of oxygen periodic • Modern atomic electron experiment atom or Bohr
in combusƟ on table of theory • Plum pudding • Discovery of atomic model
• Law of elements • Law of mulƟ ple model concept of
conservaƟ on of proporƟ ons radioacƟ ve
mass • Law of parƟ al half-life
pressures

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