Topic 8: Periodicity

Question 1

s,p,d,f blocks on periodic table

Answer 1

s - left
p- right
d- middle
f- bottom

Question 2

Atomic radius across period 3

Answer 2

Same energy level, same shielding
Extra protons, increased nuclear charge, stronger electrostatic attraction to nucleus, pulled in closer, atomic radius decreases

Question 3

I.E. across period 3

Answer 3

• general increase
• increase in nuclear charge, decrease in atomic radius

Question 4

I.E. Mg to Al

Answer 4

Al has lower I.E. than Mg (unexpected)
- Al has outer electron in 3p orbital
- Further from the nucleus so easier to remove

Question 5

I.E. P to S

Answer 5

S has lower I.E. than P (unexpected)
- S has one pair of electrons in its 3p orbital.
- These e- repulse each other
- Easier to remove than phosphorus’ unpaired electrons in its 3p orbitals.

Question 6

Trend of melting point Na-Al

Answer 6

Increases
- Metallic bonding
- Increase in charge
- Increase in delocalised electrons
- Increase in electrostatic att’n between ions and sea of delocalised electrons

Question 7

Si melting point

Answer 7

Much higher than the metals. Many strong covalent bonds in macromolecule (giant covalent structure)
Requires high energy to break the strong covalent bonds.

Question 8

Trends of melting point P-Cl

Answer 8

Lower than the metals.
Weak IMFs between molecules, vdw forces.
Larger the molecule, greater vdw forces, more energy required to overcome forces, higher melting point.
Biggest to smallest,
S8, P4, Cl2
On graph 2,1,3

Question 9

Ar melting point

Answer 9

Monatomic
Weak vdw between atoms, lowest mp