2-1:Periodicity

Question 1

How are elements arranged?

Answer 1

According to proton number

Question 2

What are the 4 blocks of the periodic table?

Answer 2

• S-block: groups 1&2
• P- block: groups 3-0
• D-block: transition metals
• f-block: radioactive elements (La, Ac and lower 2 rows)

Question 3

What is periodicity?

Answer 3

trends of physical or chemical properties or reactions
(Not groups!)

Question 4

What is the trend in atomic radius along a period and why?

Answer 4

Radius decreases
Increased nuclear charge
Similar shielding
Electrons pulled closer as charge produces greater attraction

Question 5

What is the trend in radius down group and why?

Answer 5

• increases
• more shielding
• increased distance between valence and nuclei
• overcomes increases nuclear charge
• attraction is reduced and radius increases

Question 6

Explain the trend in ionisation energy across a period

Answer 6

• increases
• atomic radius decreases
• outer electrons are held more strongly so more energy is required to remove outer electrons

Question 7

Explain the trend in ionisation energy down group

Answer 7

• decreases
• nuclear attraction decreases as shielding increases
• less energy required to remove electrons

Question 8

What does the MP of period 3 elements depend on?

Answer 8

• structure
• bond strength

Question 9

What happens to MP across period 3?

Answer 9

• Increases across Na, Mg and Al due to stronger metallic bonding (increased ES forces of attraction)
• dramatic increase for Si due to strong covalent structure
• decrease P, S, Cl due to simple covalent structure with weak van der waals (S8, P4, Cl2)
• Ar is monatomic so weakest van der waals

Question 10

Explain the trend in ionisation energy across period 3

Answer 10

• increases
• similar shielding, increases nuclear charge, decreased atomic radius
• increases to Mg
• dips at Al as 3p orbital has higher energy than 3s orbital
• increases to P
• dips at S due to electron repulsion in 3p4
• increases to At