Periodicity

Question 1

What sections of the periodic table are in the s-block?

Answer 1

Groups 1 and 2

Question 2

What sections of the periodic table are in the p-block?

Answer 2

Groups 3-8

Question 3

What sections of the periodic table are in the d-block?

Answer 3

The transition metals

Question 4

What sections of the periodic table are in the f-block?

Answer 4

The lanthanides and the actinides

Question 5

What happens to atomic radius across period 3?

Answer 5

It decreases

Question 6

Why does atomic radius decrease across period 3?

Answer 6

The nuclear charge increases which draws the outer electrons closer to the nucleus

Question 7

What happens to melting point across period 3?

Answer 7

The metallic elements increase, silicon is very high, the last 4 are low but vary based on Mr

Question 8

Why does the melting point of the metallic elements increase across period 3?

Answer 8

The number of outer shell electrons increases so more can be delocalised so there is greater attraction between metal ions and electrons

Question 9

Why is the melting point of silicon much higher than the rest of the elements in period 3?

Answer 9

Because it is a giant covalent structure and lots of energy is required to break its many strong covalent bonds

Question 10

Why are the melting points of the last 4 elements in period 3 low?

Answer 10

Because phosphorus, sulfur and chlorine are simple covalent molicules and argon exists as atoms so little energy is required to overcome the weak van der Waal’s forces between them

Question 11

How do the boiling points of the last 4 elements in period 3 vary and why?

Answer 11

There is an increase from phosphorus to sulfur then decreases to chlorine and argon because the higher the Mr the stronger the van der Waal’s and sulfur exists as S8 but phosphorus as P4 and chlorine as Cl2

Question 12

What happens to first ionisation energy across period 3?

Answer 12

It increases overall

Question 13

Which elements in don’t follow the general trend of increasing across period 3?

Answer 13

Aluminium and sulfur

Question 14

Why does aluminium have a lower than expected first ionisation energy?

Answer 14

Because it has an electron in the 3p sub-shell which is further away from the nucleus and has additional shielding so requires less energy to be removed

Question 15

Why does sulfur have a lower than expected first ionisation energy?

Answer 15

Because it has a pair of electrons in its 3p sub-shell which repel each other so less energy is required to remove on of them