There are three states of matter: gas, solid and liquid

All matter is made of atoms

An element is made up of one type of atom

A molecule is a combination of two or more atoms. (They can be the same

element or different elements)

• All atoms have a central part called a nucleus

• The nucleus is made up of two structures, protons that have a positive charge and neutrons which have no charge

• Orbiting around the nucleus are structures called electrons. They carry a negative charge. They are the smallest of the three structures

• Most atoms have the same number of electrons and protons

+

Nucleus

ElectronsNeutron

(neutral)

Protons

Atom

Periodic Table

HeHelium

2

4.0

Symbol

Element Name

Atomic Number

Atomic Weight

Periodic Table The atomic number represents the number of electrons and protons

HeHelium

2

4.0

Symbol

Element Name

Atomic Number

Atomic Weight

The number of neutrons is

calculated by subtracting the Atomic number from the Atomic

Weight

4-2 = 2 neutrons in a Helium atom