2.1 Periodicity

Question 1

What does the group number in the periodic table tell you about the number of electrons on the elements’ outer shell in that group?

Answer 1

The group number tells you the number of electrons in the outer shell.

(see page 94 in the revision guide)

Question 2

Draw where sad,p and f block are on the periodic table.

Answer 2

(see page 94 in the revision guide)

Question 3

Does the atomic radius increase or decrease across a period?

Answer 3

Atomic radii decrease as you move from left to right across a period, because the increased number of protons create more positive charge attraction for electrons which are in the same shell with similar shielding.

(see page 94 in the revision guide)
(see page 1 in the chemrevise revision guide for a graph of the trend in period 3)

Question 4

Draw a general graph for the difference in melting points across period 3.

Answer 4

(see page 95 in the revision guide)

Question 5

Does ionisation energy generally increase or decrease across a period?

Answer 5

Ionisation energy generally increases across a period. This is due to increasing number of protons as the electrons are being added to the same shell.

(see page 95 in the revision guide)

Question 6

How are elements classified into s, p, d or f block on the periodic table?

Answer 6

Elements are classified as s, p, d or f block according to which orbitals the highest energy electrons are in.

Question 7

Why is there a small drop between Mg and Al in the trend of 1st ionisation energy?

Answer 7

There is a small drop between Mg and Al. Mg has its outer electrons in the 3s sub she;; whereas Al is starting to fill the 3p sub shell. Al’s electron is slightly easier to remove because the 3p electrons are higher in energy.

Question 8

Why is there a small drop between phosphorous and sulphur in the trend of 1st ionisation energy?

Answer 8

There is a small drop between phosphorous and sulphur because Sulphur’s outer electron is being paired up with another electron in the same 3p orbital.
When the second electron is added to an orbital there is a slight repulsion between the two negatively charged electrons which makes the second electron easier to remove.

Question 9

Draw the graph for the trend in ionisation energy across period 2.

Answer 9

(see page 1 in the chemrevise revision guide)

Question 10

Draw the graph for the trend in melting and boiling points across period 2.
Explain the reason for these peaks/drops for each element.

Answer 10

(see page 1 in the chemrevise revision guide)

Question 11

Explain why S8 has a higher melting point than P4.

Answer 11

S8 has a higher melting point than P4 because it has ore electrons (S8=128) (P4=60) so has stronger van Der Waals between molecules.