Review: Elements
Elements
A pure substance made up of only
one type of atom.
 Every known element is listed on
the periodic table.
 Examples: sodium and oxygen

Physical Properties
 Any
feature of a substance, such as
an element, that can be OBSERVED
or MEASURED.
 Examples:




Colour
State (solid, liquid or gas)
Lustre (shiny or dull)
Boiling Point
Physical Properties of Sodium
 Colour?
 Silver

State?
 Solid

Lustre?
 Shiny

Boiling Point?
 883°C
Chemical Properties
Describe how substances, such as
elements, will BEHAVE when in
contact with another substance.
 Examples:

 Reactivity with oxygen
 Combustibility
 Reactivity with water
Chemical Properties of Sodium

Reactivity with water?

Reactivity with oxygen?
reactions of alkali metals
 Sodium turns white

Combustibility?
 Catches on fire very easily
Atoms


The smallest unit of an element
Made up of sub-atomic particles.
Sub-atomic
Particle
Proton
Electrical
Charge
Symbol
Location
+
p+
Nucleus
Electron
-
e-
Around the
nucleus
Neutron
Neutral
(no charge)
n0
Nucleus
Look at the Periodic Table!!!



Protons = Atomic Number
Electrons = Atomic Number
Neutrons =
Atomic Mass – Atomic Number
ATOMIC
NUMBER
ATOMIC
MASS
Atoms of Sodium



Protons = Atomic Number
Electrons = Atomic Number
Neutrons =
Atomic Mass – Atomic Number
ATOMIC
NUMBER
Protons = 11
Electrons = 11
Neutrons = 23 – 11
ATOMIC
MASS
= 12
Bohr – Rutherford Diagrams


Diagram of an atom
Remember:





Nucleus: Protons and Neutrons
Around the nucleus in shells: Electrons
1st shell: 2 electrons max
2nd shell: 8 electrons max
3rd shell: 8 electrons max
B-R of Sodium
P = 11
E = 11
N = 23 – 11
= 12
VALENCE SHELL
P = 11
N = 12
VALENCE ELECTRONS = 1