Periodic Table

Question 1

Trend of atomic radius across the period

Answer 1

• As number of protons increases, nuclear charge increases
• Increase in shielding effect negligible as successive electrons added to the same electron shell
• Increase in effective nuclear charge
• Valence electrons more strongly attracted to nucleus
• Atomic radius decreases across the period

Question 2

Trend of atomic radius down the group

Answer 2

• Down the group, nuclear charge increases as number of protons increases
• Increase in shielding effect as number of shells increases
• Valence electrons further away from nucleus, thus are less strongly attracted to the nucleus
• Atomic radius increases down the group