1. 2008
ENTER

2. 1. What’s inside an atom?
2. Table of Contents
3. Introduction
4. Structure of the Atom
5. Labelled Diagram of an Atom
6. Nature of the particles
7. Symbol of an Element
8. Atomic Number
9. Mass Number
10.Arrangement of electrons

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

4. Atoms have three basic
particles:
1. Proton
2. Neutron
3. Electron
The protons and
neutrons are found
inside the nucleus.
Key The electrons orbit the
Proton nucleus on shells.to see labelled
Click
Neutron diagram
Electron

5. shell
electron
proton
nucleus
neutron
Key
Proton
Neutron
Electron

6. Proton: large with positive
charge +
Neutron: large with no
charge 0
Electron: small with
negative charge -

7.  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
here
can be represented.
Kr Symbol of Krypton

8.  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 here to see an example.
Atomic Number 36
Kr Symbol of Krypton

9.  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 here to see how the symbol of the element
Krypton can be represented.
Mass Number 84
Atomic Number 36
Kr Symbol of Krypton

10.  Electrons are arranged in shells that move around
the nucleus situated in the centre of the atom.
Shell No. of electrons
1st shell 2 electrons
2nd shell 8 electrons
3rd shell 18 electrons
4th shell 32 electrons