1.3.5 Periodicity

Question 1

What happens to the atomic radius across a period?

Answer 1

Atomic radius decreases across a period. This is because the force of attraction increases, pulling the electrons closer to the nucleus.

Question 2

What happens to the first ionization energy across a period?

Answer 2

The first ionization energy increases. This is due to an increase in nuclear charge and a decrease in atomic radius.

Question 3

Why does Al have a lower first ionization energy than Mg?

Answer 3

Al enters a new sub-shell. Each sub-shell has higher energy, meaning less will be required to remove an electron.

Question 4

Why does S have a lower first ionization energy than P?

Answer 4

The outer electron of S pairs up on the orbital, causing slight repulsion. This means less energy is required to remove the outer electron.

Question 5

What is the trend in electronegativity across a period?

Answer 5

Electronegativity increases across a period. The closer to fluorine, the higher it will be.

Question 6

Why is there no electronegativity value for group 0?

Answer 6

All the group 0 elements have full outer shells, meaning they don’t form covelant bonds.

Question 7

What is the trend in electrical conductivity across period 3?

Answer 7

Na - Al, increase
Si, semi conductor
P - Ar, extremely low

Question 8

What is the trend in melting and boiling point across period 3?

Answer 8

Na - Si, increase

Si - Ar, decrease