Periodicity

Question 1

Describe atomic radius across a period

Answer 1

• atomic radius decreases
• this is due to an increased nuclear charge - increased proton number
• stronger forces of attraction between the outer electron and the positive nucleus

Question 2

Describe atomic radius down a group

Answer 2

• atomic radius increases
• more electrons, more shells, more shielding
• weaker forces of attraction between the outer electron and positive nucleus

Question 3

Describe ionisation energy across a period

Answer 3

• ionisation energy increases
• atomic radius decreases
• nuclear charge increases as there’s more protons
• stronger forces of attraction between the outer electron and the positive nucleus
• therefore more energy required to lose an electron

Question 4

Describe ionisation energy down a group

Answer 4

• ionisation energy decreases
• atomic radius increases
• more electrons, more shells, more shielding
• weaker forces of attraction between outer electron and nucleus
• less energy required to lose an electron

Question 5

Describe melting point across period 3 in terms of sodium, magnesium and aluminium

Answer 5

• sodium, magnesium and aluminium have metallic bonding
• melting points increase due to greater positive charged ions
• more electrons are released as free electrons
• stronger electrostatic forces of attraction increases from Na to Al

Question 6

Describe melting point across period 3 in terms of silicon

Answer 6

• silicon is macromolecular meaning it has very strong covalent structure
• covalent bonds require a lot of energy to break
• resulting in a high melting point

Question 7

Describe melting point across period 3 in terms of phosphorus, sulfur and chlorine

Answer 7

• all are simple covalent molecules
• held with weak Van Der Waals forces
• these intermolecular forces don’t require much energy to overcome
• resulting in low melting points

Question 8

Describe melting point across period 3 in terms of argon

Answer 8

• argon is a noble gas - full outer shell of electrons
• this makes the atom very stable
• Van Der Waals forces between atoms is very weak
• resulting in a low melting point