U S M A N S A N D H U

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PHYSICS OF ATOM

• Fundamental piece of matter.

• The protons and the neutrons make up the center of the atom called the nucleus and

the electrons fly around above the nucleus in a small cloud.

SUBCOMPONENTS AND QUANTUM THEORY

BOHAR MODEL OF ATOM

• The electron to move around the nucleus following fixed paths, or orbits, much as a

planet moves around the sun.

• This lowest energy state is called the ground state.

• It successfully predicted the

frequencies of the lines in the

hydrogen spectrum, so it seemed to be

valid.

MAIN POINTS OF THE BOHR MODEL

• Electrons orbit the nucleus in orbits that have a set size and energy.

• The energy of the orbit is related to its size. The lowest energy is found in the

smallest orbit.

• Radiation is absorbed or emitted when an electron moves from one orbit to another.

RUTHERFORD'S PLANETARY MODEL OF THE ATOM

• Rutherford tested Thomson's

hypothesis by devising his "gold foil"

experiment.

• Alpha particles

DISCOVERY OF THE ELECTRON

Electrons are bound to atoms they can – after

acquiring energy from their surroundings –

change their position tremendously fast.

• Chadwick’s work

DISCOVERY OF NEUTRONS

DISCOVERY OF PROTONS

The Discovery of Radioactivity (Ernest

Rutherford)

• In 1899 Ernest Rutherford studied the

absorption of radioactivity by thin

sheets of metal foil and found two

components: alpha

Radiation affected by electric and

magnetic field

THE BASIC PARTICLES THAT MAKE UP AN ATOM

• Name symbol Approximate More accurate mass

Relative charge

• Relative mass

• Proton P 1 1.0000

+1

• Neutron n 1 1.0016

0

• Electron e Almost zero 0.000547

-1

•