ATOMS AND ISOTOPES

ATOMS

BUILDING BLOCKS OF MATTER.

ATOMS COMPOSE MATTER; THEIR PROPERTIES DETERMINE MATTER’S PROPERTIES.

LEUCIPPUS

IS CREDITED AS THE PHILOSOPHER TO FIRST DEVELOP THE THEORY OF ATOMISM.

DEMOCRITUS

SUGGESTED THAT MATTER WAS ULTIMATELY COMPOSED OF SMALL, INDIVISIBLE PARTICLES CALLED ATOMOS.

ATOMOS

• GREEK WORD FOR INDIVISIBLE

DALTON’S ATOMIC THEORY

EACH ELEMENT IS COMPOSED OF TINY INDESTRUCTIBLE PARTICLE

ATOMS OF AN ELEMENT ARE IDENTICAL, HAVING THE SAME PROPERTIES SUCH AS MASS, SIZE AND CHEMICAL PROPERTIES.

JJ THOMSON

• DURING INVESTIGATIONS OF CATHODE RAYS ELECTRON WAS DISCOVERED IN 1897 BY THIS ENGLISH PHYSICIST

• HE PROPOSED THAT THE NEGATIVELY CHARGED ELECTRONS WERE HELD WITHIN A POSITIVELY CHARGED SPHERE.

• THE MODEL PROPOSED BY THIS PHYSICIST IS KNOWN A THE PLUM PUDDING MODEL.

ERNEST RUTHERFORD

• HE DIRECTED TINY, POSITIVELY CHARGED PARTICLES-CALLED ALPHA PARTICLES AT AN ULTRA THIN SHEET OF GOLD FOIL

• HE DEVELOPED THE NUCLEAR THEORY OF THE ATOM

NUCLEAR THEORY OF ATOM

• MOST OF THE ATOMS MASS AND ALL OF ITS POSITIVE CHARGE ARE CONTAINED IN A CORE CALLED NUCLEUS.

• MOST OF THE VOLUME OF THE ATOM IS EMPTY SPACE, THROUGH WHICH ELECTRONS ARE DISPERSED.

• THERE ARE ELECTRONS OUTSIDE THE NUCLEUS AND PROTONS INSIDE THE NUCLEUS, HENCE ATOM HAS NEUTRAL CHARGE.

JAMES CHADWICK

• IN 1932, HE MADE A FUNDAMENTAL DISCOVERY, HE PROVED THE EXISTENCE OF NEUTRONS.

• HE BOMBARDED A THIN SHEET OF BERYLLIUM WITH ALPHA PARTICLES

PROTONS, ELECTRONS, AND NEUTRONS

ATOMS IS CONSIST OF 3 BASIC PARTICLES

NUCLEUS

THE _________ (CENTER) OF THE ATOM CONTAINS THE PROTONS AND THE NEUTRONS

ELECTRON

THE OUTERMOST REGIONS OF THE ATOM ARE CALLED _______ SHELLS AND CONTAIN THE ELECTRONS.