THE STRUCTURE OF THE STRUCTURE OF ATOMATOM

Submitted By , Smitha M.S. Physical science Roll No: 110

Atomsan atom is the smallest particle of an element .example : “O” for oxygen.

Moleculescontains two or more atoms which are bonded together ( maybe same element or not )example : H2 and CCl4

Ions-ions are charged either positive or negative-are form in liquid or molten state-lose electron (+ ion),gain electron (- ion)example : Na+ , Mg2+ , Br-

Kinetic Theory of MatterKinetic Theory of MatterSolids

- strong forces of attraction. - particle only vibrate (fixed shape and volume)

Liquids- force of attraction weak than solid.- particle can move around (follow container shape)

Gases- no attraction between particles.- particle move faster and freely (zigzag)

John Dalton(1766-1844)John Dalton(1766-1844)

In 1808, he proposed that :

1.All matter is composed of atoms.

2.Atoms cannot be created or destroyed.

3.All the atoms of an element are identical.

4.The atoms of different elements are different.

5.When chemical reactions take place, atoms of

different elements join together to form

compound

J.J.Thomson (1856-1940)J.J.Thomson (1856-1940)

1. It was the first model of the atom.

2. 1897- Thomson discovered the

electron (negatively- charged).

3. Thomson suggested that an atom is a

positively- charged sphere with

electrons embedded in it. Its called

plum pudding model.

Ernest Rutherford (1871-Ernest Rutherford (1871-1937)1937)1. 1914- Rutherford discovered the proton

2. Rutherford model was based on the alpha

particle scattering experiment.

3. He proposed that,

1) All the positive charge of an atom is

concentrated in the nucleus

2) An atom consists of a positively-charged

nucleus with a cloud of electrons

surrounding the nucleus

Neils Bohr (1885-1962)Neils Bohr (1885-1962)

He was a student of Rutherford

He proposed that,

1) Electrons are arranged in orbits (electron

shells) around the nucleus of the atom

2) Electrons in a particular path have a fixed

energy.

To move from one orbit to another, an electron

must gain or lose the right amount of energy.

SUBATOMIC PARTICLESSUBATOMIC PARTICLES

Atoms are made of three different types of

subatomic particles called protons, neutrons

and electrons

Protons and neutrons are found in the nucleus

and they are known as nucleons

++

proton

neutronshell

electron

{nucleon

•Nucleus is positively charged because the

protons are positively charged and the

neutrons are electrically neutral.

•Electrons rotate around the nucleus in a

certain orbit called shells, just like planets

rotate around the sun.

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