2008

ENTERENTER

1. What’s inside an atom?2. Table of Contents3. Introduction4. Structure of the Atom5. Labelled Diagram of an Atom6. Nature of the particles7. Symbol of an Element8. Atomic Number9. Mass Number

10.Arrangement of electrons

After viewing this tutorial, you will be able to state the properties of electrons, protons and neutrons.

Atoms have three basic particles:1. Proton2. Neutron3. Electron

The protons and neutrons are found inside the nucleus. The electrons orbit the nucleus on shells.

Key

Proton

Neutron

Electron

Click to see labelled diagram

Key

Proton

Neutron

Electron

nucleus

shell

proton

neutron

electron

Neutron: large with no charge

Proton: large with positive charge

Electron: small with negative charge

+

-

0

An element is made up of the same kind of atoms. It can be written as a symbol. The symbol is derived from the English or the Latin names of the element. The first letter or the first two letters are used. Click here to see how the symbol of the element Krypton can be represented.

KrKr Symbol of Krypton

here

The atomic number of an element is found at the bottom left of the symbol. It tells how many protons are in the atom.

Click to see an example.

KrKrAtomic Number

Symbol of Krypton

36

here

The mass number of an element is found at the top left of the symbol. It tells the sum of the number of neutrons and protons found in the nucleus of an atom.

Click to see how the symbol of the element Krypton can be represented.

KrKrAtomic Number

Mass Number 84

Symbol of Krypton

36

here

Electrons are arranged in shells that move around the nucleus situated in the centre of the atom.

Shell No. of electrons1st shell 2 electrons

2nd shell 8 electrons3rd shell 18 electrons

4th shell 32 electrons