Periodicity Rules

Question 1

Atomic radius

Answer 1

Increases going down a group

decreases across a period (Group 1 highest, group 8 lowest)

Question 2

Ionic radius

Answer 2

Cations and anions increase in size going down a group
Ionic radius is highest in group 1 and decreases until group 5
group 7 and 8 have higher ionic radii

Question 3

Melting points

Answer 3

In group 1 the melting point decreases going down the group
(as the atoms become larger and the strength of the metallic bomb decreases)

In group 7 the melting point increases going down the group

Question 4

Electronegativity

Answer 4

Electronegativity increases from group one (Lowest) to group 8 (Highest)

Question 5

First ionization energy

Answer 5

Decreases going down a group

Increases going across a period (group one lowest group 8 highest)

Question 6

Reactivity

Answer 6

Increase is going down group 1/alkali metals

Decrease is going down group 7/halogens