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p-Block Group 13 Elements
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1
Question
What constitutes the p-block elements in the periodic table?
Answer
Groups 13 to 18, containing metals, metalloids, and non-metals
2
Question
What is the general valence shell electronic configuration of p-block elements?
Answer
ns² np¹⁻⁶
3
Question
Why does the first member of p-block groups 13-17 differ from other members?
Answer
Small size, high electronegativity, and absence of d-orbitals
4
Question
What enables the first member of p-block groups to form pπ-pπ multiple bonds?
Answer
Greater ability due to small size and availability for effective overlapping
5
Question
What is the highest oxidation state of p-block elements?
Answer
Equal to group number minus 10
6
Question
What is the inert pair effect in p-block elements?
Answer
Reluctance of ns² electrons to participate in bonding, stabilizing lower oxidation states down the group
7
Question
What is the valence shell electronic configuration of group 13 elements?
Answer
ns² np¹
8
Question
Why is the atomic radius of Ga smaller than Al?
Answer
Poor shielding by 10 d-electrons, leading to higher effective nuclear charge
9
Question
Why do ionization enthalpies not decrease smoothly down group 13?
Answer
Poor shielding by d- and f-electrons fails to compensate increased nuclear charge
10
Question
What trend is observed in electronegativity down group 13?
Answer
Decreases from B to Al, then increases marginally due to atomic size discrepancies
11
Question
Why is boron non-metallic while heavier group 13 elements are metallic?
Answer
High ionization enthalpy and small size favor covalent bonding in boron
12
Question
What is the common oxidation state for group 13 elements?
Answer
+3, with +1 becoming more stable down the group due to inert pair effect
13
Question
Why do group 13 trihalides behave as Lewis acids?
Answer
Electron deficient, with only six electrons around the central atom
14
Question
How does the Lewis acid strength of group 13 trihalides vary down the group?
Answer
Decreases with increasing size of the central atom
15
Question
What protects aluminium from further oxidation in air?
Answer
Thin protective layer of Al₂O₃
16
Question
What is the nature of oxides down group 13?
Answer
Acidic for B₂O₃, amphoteric for Al₂O₃ and Ga₂O₃, basic for In₂O₃ and Tl₂O₃
17
Question
Why does aluminium show amphoteric character?
Answer
Dissolves in both acids and alkalies
18
Question
What happens when aluminium reacts with dilute HCl?
Answer
Forms Al³⁺ and liberates H₂: 2Al + 6HCl → 2Al³⁺ + 6Cl⁻ + 3H₂
19
Question
Why is concentrated HNO₃ ineffective on aluminium?
Answer
Forms protective oxide layer, rendering it passive
20
Question
What product forms when aluminium reacts with aqueous NaOH?
Answer
Sodium tetrahydroxoaluminate: 2Al + 2NaOH + 6H₂O → 2[Al(OH)₄]⁻ + 3H₂
21
Question
What is the maximum covalence of boron and why?
Answer
4, due to absence of d-orbitals
22
Question
What are the natural sources of boron?
Answer
Borax (Na₂B₄O₇·10H₂O), boric acid (H₃BO₃), kernite, colemanite
23
Question
How is boron extracted by electrolytic method?
Answer
Electrolysis of fused MgO, MgF₂, and B₂O₃ at 1100°C
24
Question
What is the structure of elemental boron?
Answer
Clusters of B₁₂ icosahedral units
25
Question
Why is amorphous boron more reactive than crystalline?
Answer
Less compact structure allows easier attack
26
Question
What product forms when boron burns in oxygen?
Answer
B₂O₃: 4B + 3O₂ → 2B₂O₃
27
Question
How does boron react with fused NaOH?
Answer
Forms sodium metaborate: 2B + 6NaOH → 2Na₃BO₃ + 3H₂
28
Question
What is the anhydride of boric acid?
Answer
Boron trioxide, B₂O₃
29
Question
How is B₂O₃ prepared from boric acid?
Answer
Heating: H₃BO₃ → HBO₂ → H₂B₄O₇ → B₂O₃
30
Question
What is the nature of B₂O₃?
Answer
Acidic oxide, forms borates with bases