C8- Periodicity

Question 1

What is periodicity?

Answer 1

The term periodicity describes a repeating pattern in properties of elements across periods of the periodic table.

Question 2

What is the trend of period 3 atomic radius?

Answer 2

Decrease due to the increase on proton number therefore stronger attraction pulling electrons closer the same level of shielding.

Question 3

What is the trend of boiling point of melting and boiling points of period 3?

Answer 3

Na-Al (stronger metallic bonds)

• This is because the number of outer (highest energy level) electrons increases
• so, more electrons can be delocalised leading to a greater attraction between positive ions and delocalised electrons.
• The size of the ions decreases from Na+ to Mg2+ to Al3+ and this again leads to a greater attraction between the smaller ions and the delocalised electrons.
• More energy is needed to break the stronger metallic bonds, so melting and boiling points are higher.

Silicon (giant covalent structure)

• Silicon has a giant covalent structure.
• This means that a large amount of energy is required to break the many strong covalent bonds.
• For this reason, the melting and boiling points of silicon are very high.

P-Cl (Relative atomic mass)

• This is because they are either simple molecules (P4, S8, Cl2)
• There are only weak van der Waals forces holding the molecules or atoms together.
• Breaking these forces of attraction does not require a lot of energy and therefore their melting and boiling points are low.

Argon

Monatomic and only weak van der Waals forces hold the atom together.

Question 4

Trend in First Ionisation Energy

Answer 4

General increase due to increase in proton number so greater force of attraction.

Exceptions: Aluminium removing electron from a higher energy orbital is easier.
Sulphur mutual repulsion between paired electrons means less energy is required to remove one of them.