Periodicity

Question 1

What is periodicity?

Answer 1

The repeated pattern/trend in properties down or across the periodic table

Question 2

How do the melting points change across the 2nd period and why?

Answer 2

Na to Al rise as metals delocalise outer electrons so they have more electrostatic attraction between negative electrons and positive ions

Si highest as giant covalent structure with many strong covalent bonds between atoms

P4,S8,Cl2 low as weak intermolecular forces between molecules but S8 is largest with most electrons so highest M.P of the 3

Question 3

How does atom radius change down a group and why?

Answer 3

Radius increase as you go down a group because there are more occupied electron shells

Question 4

How does the atomic radius change across a period?

Answer 4

Gradually decreases as all elements have the same “shell” occupied but the nuclear charge increased, the attraction is stronger between electrons and nucleus
Shielding doesn’t change significantly