3.2.1 Periodicity

Question 1

How are elements in periodic table arranged?

Answer 1

Increasing proton number

Question 2

What block are group 1 and 2 elements?

Answer 2

S-block

Question 3

What block are group 3-0 elements?

Answer 3

p-block

Question 4

What block are transition elements?

Answer 4

d-block

Question 5

How does atomic radius change across period 3, why?

Answer 5

The number of protons increases however shielding remains constant. Leads to a greater electrostatic attraction between nucleus and outermost electron. So the atomic radius decreases.

Question 6

Define first ionisation energy?

Answer 6

Energy required to remove the outermost electron from one mole of gaseous atoms to form one mole of gaseous ions.

Question 7

What factors affect the ionisation energy?

Answer 7

Atomic radius
Amount of shielding
Nuclear charge

Question 8

State the trend in ionisation energy across period 3.

Answer 8

Ionisation energy Increases, number of protons increases but shielding remains the same so increasing electrostatic attraction between outermost electron and the nucleus.

Question 9

State the trend in ionisation energy down a group.

Answer 9

Ionisation energy decreases, the amount of inner energy level shielding increases so the amount of electrostatic attraction to the nucleus decreases.

Question 10

Why is there a drop in ionisation energy between group 2 and 3?

Answer 10

In group 3 each element has an electron in the P-sublevel. In group 2 the outermost electron is in the s-sublevel. P-sublevel is higher in energy so requires less energy to remove the outermost electron compared to s-sublevel.

Question 11

Why is there a drop in ionisation energy between group 5 and 6?

Answer 11

The 4th electron has to enter an already half filled p-orbital causing electrons to pair up. This leads to an electron pair repulsion which makes it easier to remove the fourth outer electron.