2.5 Explaining Trends

Question 1

What happens to atoms going down a group?

Answer 1

The number of shells occupied by electrons increases by one extra electron per shell per period. This has 2 effects:
- larger atoms lose electrons more easily going down a group
- larger atoms gains electrons less easily going down a group
This happens because the outer electrons are further away from the attractive force of the nucleus. Also, the inner shell of electrons shields the outer electrons from the positive charge of the nucleus

Question 2

Why does reactivity increase going down Group 1?

Answer 2

Because the atoms get larger so the single electron in the outermost shell is attracted less strongly to the positive nucleus.
Also, the outer electron experiences a shielding effect from inner shells of electrons.
Nuclear charge increases going down the group as more protons are present in the group. However, the greater distance and shielding effect outweigh the increased nuclear charge

Question 3

Why does reactivity decrease going down Group 7?

Answer 3

Going down the group the outermost electrons get further away from the nucleus so it is harder to attract an extra incoming electron. The outer shell will also be shielded by more inner shells of electrons reducing electrostatic attractions.