Periodicity

Question 1

What is periodicity?

Answer 1

The repeating trend of properties across different periods with increasing atomic number.

Question 2

What is a horizontal trend?

Answer 2

Trends across a period

Question 3

What is the name for a trend down a group?

Answer 3

Vertical trend

Question 4

What is the trend in atomic radius across a period and down a group?

Answer 4

Across period-
DECREASES
As nuclear charge increases so greater attraction between electrons and nucleus
Same shielding

Down a group-
INCREASES
As more shielding
Smaller attraction as outer shell further away

Question 5

What is the trend in 1st ionisation energy across a period and down a group?

Answer 5

Across a period-
General INCREASE
Smaller atomic radio so outer electron closer and larger nuclear charge so greater attraction
Same shielding

Down a group-
DECREASE
Larger atomic radii so outer electron is further from the nucleus so weaker attraction
More shielding

Question 6

What is the trend in melting points across period 2 and 3?

Answer 6

Group 1-4 there is an increase
(Group 1-2 or 3) metallic bond strength increases as stronger attraction due to larger nuclear charge
(Group 2-3 or 3-4) increases again as giant covalent structures with very strong covalent bonds

Group 4-5678Decrease
As group 4 have strong covalent bonds where as group 5 onwards have weak London forces between the molecules

Question 7

In group 3 what is the trend in melting point in groups 5-8?

P4, S8, Cl2, Ar

Answer 7

Highest- S8
P4
Cl2
Ar
As they decrease in size so have less electrons so strength of attraction decreases so melting point decreases