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Period 3
27 December 2012
19:29

Metals- Na, Mg and Al conduct electricity
- Sea of delocalised electrons that surround cations
are free to move and carry charge when a potential
difference is applied

Silicon a metalloid
- Few electrons have enough energy to enter higher energy level
at r
...
t
energy to break the
electrostatic
attraction between
the cations and the
sea of delocalised
electrons
- Melting temp is
higher of Al than Na
because it has more
electrons so the
attraction is greater

Na

Mg

Semi conductor

Al

Si

P

S

Cl

Ar

Very low m
...
t

Metallic

Giant
covalent

Atomic radii decreases across the period
Additional protons
The nuclear charge increases
More electrons in outermost shell
Held less tightly
Radii decreases

Intermolecular

As it is monoatomic, it has very
weak Van der Waals forces

Low m
...
t than Cl and P because it has more
atoms in the molecule so it has stronger Van der Waals forces

Ionisation energy generally increases
-

More protons in nucleus
Nuclear charge is greater
The attraction between the outermost electron and the nuclei increases
Constant shielding
Increasing ionisation energy

Fall at Aluminium
-

P orbital- outermost electron for Al
S orbital- Mg
Al is more distant from the nuclei than Mg
P orbital is shielded by the s orbital and inner shells
Ionisation energy decreases

Fall at Sulphur
-

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