The smallest particle of an element and not breakable anymore.

Examples:Atom of hydrogen atom of magnesium atom of oxygen atom of chlorine

H

Mg

Cl

O

Particle theory

Usually made up of two or more elements which are chemically

bonded together

Matter

A group of two @ more atoms, which might consist of: one type of element (Element)

@ different types of element (Compound)

Examples of element molecules:Molecule of hydrogen gas

Molecule of oxygen gas

Molecule of chlorine gasOO

Cl Cl

H H

Examples of compound molecules:

Molecule of water, H2O

Molecule of ammonia, NH3

Molecule of ethanol, C2H5OH

HH

O

H

HH N

O

C CH

H

H

HH

HParticle theory

Ions are atoms which have charge

Positively-charged ion /cation (loss e-)

Negatively charged ion / anion (gain e-)

+

-

Hydrogen atom Hydrogen ion

Magnesium atom Magnesium ion

Oxygen atom Oxide ion

Chlorine atom Chlorine ion

Particle theory

H+HLose electron

Mg2+Lose electronMg

O2

-

Gain electronO

Cl-

Gain electronCl

Symbol of element

Examples of ions:

Subatomic Particle In An Atom

Proton Electron

Neutron

Nucleus of atom Electron

shells

ARRANGEMENT OF SHELLS IN AN ATOM

NUCLEUS

2 ELECTRONS

8 ELECTRONS

8 ELECTRONS

18 ELECTRONS

1

23

4

Electron arrangement in the carbon atom

C12

6

proton number = 6

number of protons = 6

number of electrons = 6

2 . 4

= electron

nucleus

Number of valence electrons = 4

• Proton number (p) – number of protons in the nucleus of atom

• Nucleon number (p+n)–total number of protons and neutrons in the nucleus of atom

2.3 ISOTOPES

• Isotopes is just like twins, same genetic but different of DNA

• atoms of the same element with same number of protons but different number of neutrons

What is isotopes?

Examples of Isotopes• Take a look at Wikipedia isotopes table

• Hydrogen :

• Graphite :

• Oxygen :

1

1

H 3

1

H2

1

H

12

6C

14

6C13

6C

16

8O

18

8O17

8O

Isotopes of Hydrogen

Hydrogen :

1

1

H

2

1

H

3

1

H