IC01: the periodic table (period 3)

Question 1

trend of atomic radius

Answer 1

atomic radii decrease down the group due to increase nuclear charge, relatively same shielding effect = outermost electron shell is more closely attracted to the nucleus

Question 2

trend of ionic radius

Answer 2

falls from Na to Al (forms cation) then rises from S to Cl (forms anion)

Question 3

first IE trend

Answer 3

generally increases
- increases from Na to Mg
then dips at Al due to removal of electron from a lower 3p orbital shell
-then increases again from Al to S
dips at S due to removal of pair 3px electron; experiences inter-electronic repulsion
- then increases again

Question 4

trend of melting point

Answer 4

giant metallic structure: Na - Al, melting point increases as string metallic bond between larger seas of delocalised electron and more positively charges cation

giant molecular structure, Si : highest melting point due to strong covalent bonds

simple molecular structure: S8 > P4 > Cl2 >Ar
size of electron cloud

Question 5

trend of electrical conductivity

Answer 5

metal: Na - Al, electrical conductivity rises due to more number of delocalised electrons to act as charge carriers

metalloid, S: electrical conductivity falls

insulators (P, S, Cl, Ar): no electrical conductivity

Question 6

metal reaction with oxygen (Na, Mg, Al)

Answer 6

basic -> amphoteric
pH 13: 2 Na(s) + 1/2 O2 (g) -> Na2O (s)
pH 8: Mg(s) + 1/2 O2 (g) -> MgO (s)
pH 7 (insoluble): 2Al(s) + 3/2 O2 (g) -> Al2O3

Question 7

non metals reaction with oxygen

Answer 7

amphoteric -> acidic

pH 7 (insoluble): Si + O2 -> SiO2
pH 3: P4 + 3O2 -> P4O6 (H3PO3)
pH 2: P4 + 5O2 -> P4O10 (H3PO4)
pH 2: S + O2 -> SO2 (H2SO3)
pH 1: S + 3/2 O2 -> SO3 (H2SO4)

Question 8

metal reaction with chlorine (Na, Mg, Al)

Answer 8

neutral to acidic (pH7 -3)
- Na + 1/2 Cl2 -> NaCl
- Mg + Cl2 -> MgCl2 ([Mg(H2O)5(OH)]+ + H3O+)
- Al + 3/2 Cl2 -> AlCl3 (or Al2Cl6)
excess H2O: ([Al(H2O)5(OH)]2+ + H3O+)
limited H2O: Al(OH)3 + HCl

Question 9

non metal reaction with chlorine (Si, P, S)

Answer 9

acidic (pH 2-1)
- Si + 2Cl2 -> SiCl4 (SiO2 + 4HCl)
- P4 + 6Cl2 -> 4 PCl3 (H3PO3 + HCl)
- P4 + 10Cl2 -> 4 PCl5 (H3PO4 + HCl)