3.2.1 - periodicity

Question 1

Periodicity is …

Answer 1

is the repeating pattern of physical or chemical properties going across the periods

Question 2

Elements are classified into d p s elements based on

Answer 2

Which orbitals the highest energy electrons are in

Question 3

Trend in atomic radius across a period

Answer 3

Atomic radii decrease 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.

Question 4

General trend of ionisation energies across period 3

Answer 4

Ionisation energy increases across a period

Question 5

Why is there a general increase in ionisation energy across period 3

Answer 5

There is a general trend across to increase. This is due to increasing number of protons giving increased nuclear charge and increased electrostatic attraction
Similar shielding effect
Atomic radii slightly decreases
So e- more easier to remove

Question 6

Anomalies in period 3

Answer 6

Mg to Al
P to S

Question 7

Why is there a drop in ionisation energy from magnesium to aluminium

Answer 7

Mg has its outer electrons in the 3s sub shell, whereas Al is starting to fill the 3p subshell. Al’s electron is slightly easier to remove because the 3p electrons are higher in higher energy level. Further dist from nucleus so less electrostatic attraction

Question 8

Why is there a small drop in ionisation energy from P to S

Answer 8

There is a small drop between phosphorous and sulfur. Sulfur’s outer electron is being paired up with an another electron in the same 3p orbital, in phosphorus the electron is in a singularly occupied 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 - req less energy

Question 9

Describe trends in melting points across period 3

Answer 9

Increases from na to mg to al
Steep increase from na to mg , mg to al kind of on same level
Silicon is the peak
Then decreases to phos slight increase at sulphur then decrease again to cl and ar

Question 10

Explain trends in mp across period 3

Answer 10

Na to mg to al due to increase in strength of metallic bonding due to increasing nuclear charge increasing number of delocalised electrons and decreased radius
Silicon is the peak due to its giant covalent structure and strong covalent bonds
P, s, cl, ar
All simple covalent structures so have lowest values
Slight increase from p to s and decrease from cl to argon
This is bc sulfur - biggest molecule
Argon is lower bc its monatomic - weak vdw

Question 11

S block includes which groups of elements

Answer 11

Group 1 and group 2

Question 12

What element in period 3 forms oxide which is insoluble in water

Answer 12

Al2O3