The atom

Atoms

• Democritus 460BC – 370BC cutting copper wire in half, last bit atom

• Atoms are thought of as the smallest part of an element

• They are formed from three different sub-atomic particles

• These are call protons, neutrons and electrons

The sub-atomic particles

Particle Charge Mass

Proton

Electron

Neutron

Complete the following table

+1

-1

0

1

1

1/1850

The Atom

This is the nucleus

It contains all the protons

and neutrons

This is one electron

Electrons are always present

in shells

C6

12

Atomic Number

All elements on the periodic table

are shown like this

This is the elements symbol

This is carbon

This is the elements

atomic number

What does the atomic number tell us?

• The atomic number tells us how many protons an element’s atom has. This is the same as the number of electrons

• So carbon has 6 electrons

• Sodium’s atomic number is 11. So it has 11 electrons

• Oxygen has an atomic number of 8. how many electrons does it have?

• How many electrons does chlorine have

• Which has more electrons bromine or calcium?

Electron Shells

The first electron shell can have up to two electrons

The second electron shell can have up to eight electrons

The third electron shell can have up to eight electrons

Carbon’s Electron Shells

Carbon has 6 electrons

Two electrons can go in the

first shell

There are four electrons leftThese can go

into the 2nd shell

The electron configuration is written as 2. 4

The outer shell

• The number of electrons in the outer shell of an atom is the same as the group of the atom

• For example, carbon has four electrons in its outer shell and it is in group four

Question Time

23

Na11

56

Fe26

119

Sn50

19

F9

27

Al13

11 26 50 9 13

How many protons do the following elements contain?

Question Time

Question Time

Make your own atom