Periodicity

Question 1

What happens to the ionisation energy down a group?

Answer 1

• Decreases.
• More shells/ energy levels.
• Greater distance between nucleus and outer electron Increased amount of shielding.
• So weaker force of attraction between nucleus and outer shell electrons.
• So less energy required to remove on electron from outer shell.

Question 2

What happens to the atomic radius across a period?

Answer 2

• Decreases.
• Outer electrons are in the same shell.
• More protons in the nucleus.
• Same amount of shielding.
• So stronger force of attraction between the outer electrons and nucleus.
• Outer electrons pulls closer to the nucleus.

Question 3

What happens to the atomic radius down a group?

Answer 3

• Increases
• More shells of electrons
• Greater distance between the nucleus and the outer electrons
• Increase shielding
• Weak force of attraction (electrons pulled in less by nucleus)
• Outer electrons shell further away.

Question 4

What happens to the ionisation energy across a group?

Answer 4

General Trend:

• More protons
• Atoms get smaller
• Same shielding
• Therefore stronger attraction from nucleus to electrons in outer shell
• More difficult to remove

Question 5

Why does the element aluminum deviate from the trend?

Answer 5

The outer elelctron is in the 3p orbital rather than the 3s orbital which is higher energy so it’s easier to lose an electron.

Question 6

Why does the element sulfur deviate from the trend?

Answer 6

It has two of it p-electrons paired in a p-orbtial so one of these will be easier to remove than unparied one due to the replusion of the other electron in the same orbital.

Question 7

Describe the melting and boiling points across the period (Na,Mg,Al)

Answer 7

• All are have giant metallic bonding.
• Stronger attraction between metal ions and delocalised electrons as:
  
  • Higher charge
  • More deloccalised electrons
  • Smaller ions

Question 8

Describe/explain the melting and boiling points for silicon.

Answer 8

• It is a giant covalent lattice
• Highest melting and boiling point
• Many strong covalent bonds that are difficult to break

Question 9

Describe/explain the melting and boiling points for P₄, S₈ and Cl_2.

Answer 9

• They all have a simple molecular structure
• They’ve weak van der Waals’ forces between molecules
• S₈ > P₄ > Cl₂ (bigger molecules, more electrons and vdW)
• Sulfur is the strongest out of these 3 but the weakest out of the previous 4 elements.

Question 10

Describe/explain the melting and boiling points for Ar.

Answer 10

• Lowest across the whole of the period.
• Very weak can der Waals’ forces between atoms