Atomic Structure, History of the Atom

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Slide 10

Bohr’s Atom

electrons in orbits

nucleus

Slide 11

Helium atom

+

N

N

+

-

-

proton

electron

neutron

Shell

What do these particles consist of?

Slide 12

Atomic structure

Particle

proton

neutron

electron

Charge

+ ve charge

-ve charge

No charge

1

1

nil

Mass

Slide 13

ATOMIC STRUCTURE

the number of protons in an atom

the number of protons and

neutrons in an atom

He

2

4

Atomic mass

Atomic number

number of electrons = number of protons

Slide 14

ATOMIC STRUCTURE

Electrons are arranged in Energy Levels or Shells around the nucleus of an atom.

first shell a maximum of 2 electrons

second shell a maximum of 8 electrons

third shell a maximum of 8 electrons

Slide 15

ATOMIC STRUCTURE

There are two ways to represent the atomic structure of an element or compound;

1. Electronic Configuration

2. Dot & Cross Diagrams

Slide 16

Electronic configuration

With electronic configuration elements are represented numerically by the number of electrons in their shells and number of shells. For example;

N

Nitrogen

7

14

2 in 1st shell

5 in 2nd shell

configuration = 2 , 5

2 + 5 = 7

Slide 17

ELECTRONIC CONFIGURATION

Write the electronic configuration for the following elements;

Ca

O

Cl

Si

Na

20

40

11

23

8

17

16

35

14

28

B

11

5

a)

b)

c)

d)

e)

f)

2,8,8,2

2,8,1

2,8,7

2,8,4

2,3

2,6

Slide 18

Dot & Cross diagrams

With Dot & Cross diagrams elements and compounds are represented by Dots or Crosses to show electrons, and circles to show the shells. For example;

Nitrogen

N

X

X

X

X

X

X

X

N

7

14

Slide 19

DOT & CROSS DIAGRAMS

Draw the Dot & Cross diagrams for the following elements;

O

Cl

8

17

16

35

a)