Topic 1.2 Periodicity

Question 1

Along period (mpt)

Answer 1

mpt/bpt increases then decreases
(increases- with metallic bonding)
(decreases- with covalent bonding)

Question 2

Trend on melting/boiling point across

Answer 2

The bigger the ion: 1+, 2+, 3+… the stronger the attraction towards the sea of delocalised electrons so harder to break when melting.

Question 3

Atomic radius across

Answer 3

Atomic radius decreases along a period
-More protons-> bigger nuclear attraction-> pulls electron closer-> smaller atomic radius
(the bigger the atomic number, the smaller the atomic radius).

Question 4

Successive ionisation energies pattern: across a period

Answer 4

-Nuclear charge increases
-Slight decrease in atomic radius
-Slight but negligible increase in shielding
This leads to a decrease in energy of the outermost electron and a general increase in ionisation energy across the period.

Question 5

Successive ionisation energies pattern: down a group

Answer 5

-Nuclear charge increases but:
-each quantum shell is higher energy
-huge increase in atomic radius which partially
counteract the increase in nuclear charge
-huge increase in shielding
The increases in shielding and atomic radius lead to a general decrease in IE down a group.