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HRIDAYANKA

IX

BK.V.No.2

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CONTENTSATOMSDALTONS ATOMIC THEORY

STRUCTURE OF AN ATOM

HYDROGEN

CARBON

SODIUMCALCIUM

COPPER

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DALTONS ATOMIC THEORY All matter is made of very tiny particles called

atoms. Atoms are indivisible particles, which cannot be

created or destroyed in a chemical reaction. Atoms of a given element are identical in mass

and chemical properties. Atoms of different elements have different masses

and chemical properties. Atoms combine in the ratio of small whole

numbers to form compounds. The relative number and kinds of atoms are

constant in a given compound.

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ATOM

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RUTHERFORDS MODEL OF ATOM There is a positively

charged centre in an atomcalled the nucleus. Nearly

all the mass of an atomresides in the nucleus.

The electrons revolvearound the nucleus in well

defined orbits. The size of the nucleus is

very small as compared tothe size of the atom.

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BOHRS MODEL OF ATOM

Nucleus is composed ofprotons and neutrons. Protons and electrons have

equal and oppositeelectrical charges.

Only certain special orbitsknown as discrete orbits ofelectrons, are allowedinside the atom.

While revolving in discrete

orbits the electrons do notradiate energy. These orbits are called

energy levels and arerepresented by the letters

K,L,M,N... .

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STRUCTURE OF HYDROGEN ATOM

NAME HYDROGEN

SYMBOL H

ATOMIC No. 1

MASS No. 1

NUMBER OFPROTONS

1

NUMBER OFNEUTRONS

---

NUMBER OFELECTRONS

1

ELECTRONS INK - SHELL

1

VALENCY 1

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STRUCTURE OF CARBON ATOM

NAME CARBON

SYMBOL CATOMIC No. 6

MASS No. 12

NUMBER OFPROTONS

6

NUMBER OFNEUTRONS

6

NUMBER OFELECTRONS

6

ELECTRONS INK - SHELL

2

ELECTRONS INL - SHELL

4

VALENCY 4

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STRUCTURE OF SODIUM ATOM

NAME SODIUM

SYMBOL Na

ATOMIC No. 11

MASS No. 23

NUMBER OFPROTONS

11

NUMBER OF

NEUTRONS

12

NUMBER OFELECTRONS

11

ELECTRONS INK - SHELL

2

ELECTRONS INL - SHELL

8

ELECTRONS INM- SHELL

1

VALENCY 1

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STRUCTURE OF CALCIUM ATOM

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STRUCTURE OF CALCIUM ATOMNAME CALCIUM

SYMBOL Ca

ATOMIC No. 20

MASS No. 40

NUMBER OFPROTONS

20

NUMBER OFNEUTRONS

20

NUMBER OFELECTRONS

20

ELECTRONS INK - SHELL

2

ELECTRONS INL - SHELL8

ELECTRONS INM- SHELL

8

ELECTRONS INN - SHELL

2

VALENCY 2

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STRUCTURE OF COPPER ATOM

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STRUCTURE OF COPPER ATOMNAME COPPER

SYMBOL Cu

ATOMIC No. 29

MASS No. 64

NUMBER OFPROTONS

29

NUMBER OFNEUTRONS

35

NUMBER OFELECTRONS

29

ELECTRONS INK - SHELL

2

ELECTRONS INL - SHELL8

ELECTRONS INM- SHELL

18

ELECTRONS INN - SHELL

1

VALENCY 1

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