8 Periodic Table

Question 1

Periodic trend

Answer 1

Across period, atomic radii decreases
increase in nuclear charge, shielding effect by inner pqs remains relatively constant -> increase in effective nuclear charge

Question 2

Group trend

Answer 2

Down a Group, atomic radii increase
increase in nuclear charge cancelled out by increase in shielding effect
Since more pqs, larger atomic radius

Question 3

Electrical conductivities across Period 3

Answer 3

Na, Mg, Al:
Electrical conductivities are high (giant metallic lattice structures)
Increases from Na to Al (number of delocalized electrons increases from Na to Al)
Si:
Electrical conductivity decreases sharply
Giant covalent structure (But is a semi-conductor)
P4, S8, Cl2, Ar:
P to Cl have simple covalent structure
Ar has a monoatomic structure
No mobile charge carriers

Question 4

IE across Period

Answer 4

Generally increases except:
Group 2-13 and Group 15-16

Question 5

Melting point across Period 3

Answer 5

Na, Mg, Al:
Fairly high (giant metallic lattice structures), increases from Na to Al (number of valence electrons increases from Na to Al)
Si:
Highest melting point (giant covalent structure)
P4, S8, Cl2, Ar:
P to Cl have simple covalent structure
Ar has a monoatomic structure
Low melting points
S8>P4>Cl2>Ar
Greater number of electrons in molecules=Stronger id-id interactions

Question 6

Reaction with NaCl and water

Answer 6

Dissolves readily to form neutral solution (pH=7)
Only hydration of ions occurs
No hydrolysis of Na+ -> low charge density of Na -> low polarising power

Question 7

Reaction with MgCl2 and water

Answer 7

Dissolves readily to form weakly acidic solution (pH=6.5)
Hydration of ions occurs
Partial hydrolysis of Mg2+ occurs

Question 8

Reaction with Al2Cl3 and water

Answer 8

Dissolves readily to form acidic solution (pH=3)
Hydration of ions occur
Substantial hydrolysis of Al3+ occurs

Question 9

Reaction with SiCl4 and water

Answer 9

Dissolves to form a strongly acidic solution (pH=2)
Hydrolysis occurs due to energetically accessible vacant 3d orbitals for dative bonding

Question 10

Reaction with CCl4 and water

Answer 10

No reaction (does not undergo hydrolysis)
Smaller size of C atom as compared to Cl atom hinders approach of water molecules
C does not have energetically accessible vacant 3d orbitals

Question 11

Reaction with PCl5 and water

Answer 11

Undergoes hydrolysis to give strongly acidic solution (pH=2)
P atom uses energetically accessible 3d orbitals for dative bonding with water molecules

Question 12

Reaction with Na2O and water

Answer 12

Reacts vigorously to from NaOH(aq) which is strongly alkaline (pH=13)

Question 13

Reaction with Na2O and acid/base

Answer 13

Na2O is basic -> no reaction with base
Reacts with acid to form salt and water

Question 14

Reaction with MgO and water

Answer 14

Reacts vigorously to from Mg(OH)2(aq) which is weakly alkaline (pH=8)

Question 15

Reaction with MgO and acid/base

Answer 15

MgO is basic -> no reaction with base
Reacts with acid to form salt and water

Question 16

Reaction with Al2O3 and water

Answer 16

Insoluble
Energy released during hydration < energy required to overcome strong electrostatic forces of attraction between Al3+ and O2-

Question 17

Reaction with Al2O3 and acid/base

Answer 17

Al2O3 is amphoteric
Reacts with both to give salt and water

Question 18

Reaction with SiO2 and water

Answer 18

Insoluble
Large amount of energy required to break covalent bonds

Question 19

Reaction with SiO2 and acid/base

Answer 19

SiO2 is acidic
Reacts with concentrated alkali to give salt and water

Question 20

Reaction with P4O10 and water

Answer 20

Reacts violently with water to form acidic solution (pH=2)

Question 21

Reaction with P4O10 and acid/base

Answer 21

P4O10 is acidic
Reacts violently with alkali to give salt and water

Question 22

Reaction with SO3 and water

Answer 22

Reacts wo form acidic solution (pH=2)

Question 23

Reaction with SO3 and acid/base

Answer 23

SO3 is acidic
Reacts with alkali to give salt and water

Question 24

Thermal decomposition of Group 2 carbonates, nitrates and hydroxides

Answer 24

Metal cation polarizes large electron cloud of anion to such an extent that the covalent bond of the anion is weakened
Down the Group, atomic radius increases -> charge density decreases -> polarizing power decreases -> covalent bonds of anion weakened to a smaller extent

Question 25

Boiling points down Group 17

Answer 25

Down the Group, number of electrons increases, more energy required to overcome stronger id-id interactions, increase in boiling point and decrease in volatility

Question 26

Oxidizing power down Group 17

Answer 26

Decreases down a group

Question 27

Solubility of hydrogen halides

Answer 27

Dissolves in non-polar solvent (retains covalent character)
Dissolves in polar solvents (dissociates to form strong acids)

Question 28

Boiling points of hydrogen halides

Answer 28

HF (exception): highest due to presence of stronger hydrogen bonds
Down the Group: increases due to larger number of electrons -> stronger id-id interactions

Question 29

Thermal stability of hydrogen halides

Answer 29

Decreases due to decreasing bond energy

Question 30

Bond length of hydrogen halides

Answer 30

Increases down the group