Vidaara.orgClass 11 · Chemistry
CodeVID-C11-03-T3-01
Periodicity in Properties — Assignment
Name: ____________________
Roll No.: __________
Date: ____________
General Instructions
- All questions are compulsory.
- Section A carries 1 mark each, Section B 2 marks, Section C 3 marks and Section D 5 marks.
- Show full working for Sections B, C and D; only final answers are provided.
Section A — Multiple Choice Questions
5 × 1 = 5 marks
1.
The highest oxidation state of chlorine is:
- A.+1
- B.+5
- C.+7
- D.+3
2.
An oxide reacting with both acids and bases is called:
- A.basic
- B.acidic
- C.neutral
- D.amphoteric
3.
The most metallic element among these is:
- A.Na
- B.K
- C.Mg
- D.Al
4.
Which is a metalloid?
- A.Na
- B.Si
- C.Cl
- D.Ca
5.
$\text{SO}_3$ dissolved in water gives a solution that is:
- A.basic
- B.neutral
- C.acidic
- D.amphoteric
Section B — Short Answer (2 marks)
3 × 2 = 6 marks
6.
Why is the maximum covalency of second-period elements limited to 4?
7.
Write equations showing ZnO (or Al2O3) is amphoteric.
8.
Arrange Na, Mg, Al in decreasing metallic character.
Section C — Long Answer (3 marks)
2 × 3 = 6 marks
9.
Explain the anomalous behaviour of the first member of a group with reference to nitrogen.
10.
Describe how the nature of oxides changes across period 3.
Section D — Detailed Answer (5 marks)
1 × 5 = 5 marks
11.
Discuss periodicity in valence/oxidation states, metallic-non-metallic character and reactivity across a period and down a group, with examples.
Answer Key
Section A — Multiple Choice Questions
- (C) +7
- (D) amphoteric
- (B) K
- (B) Si
- (C) acidic
Section B — Short Answer (2 marks)
- Their valence shell ($n=2$) has only $2s$ and $2p$ orbitals; with no valence $d$ orbitals available, covalency cannot exceed 4.
- $\text{Al}_2\text{O}_3 + 6\text{HCl} \rightarrow 2\text{AlCl}_3 + 3\text{H}_2\text{O}$ and $\text{Al}_2\text{O}_3 + 2\text{NaOH} \rightarrow 2\text{NaAlO}_2 + \text{H}_2\text{O}$.
- Na > Mg > Al (metallic character decreases across a period).
Section C — Long Answer (3 marks)
- N is small, highly electronegative and lacks valence $d$ orbitals, so its covalency is capped at 4 (NCl3 not NCl5) and it forms strong $p\pi$-$p\pi$ multiple bonds (N≡N) unlike heavier P.
- From basic ($\text{Na}_2\text{O}, \text{MgO}$) to amphoteric ($\text{Al}_2\text{O}_3$) to acidic ($\text{SiO}_2, \text{P}_4\text{O}_{10}, \text{SO}_3, \text{Cl}_2\text{O}_7$), as metallic character decreases.
Section D — Detailed Answer (5 marks)
- Across period 3 the highest oxidation state rises +1 to +7 (Na to Cl); metallic character falls (Na metal to Cl non-metal); reactivity is high at both ends. Down a group, metallic character and reactivity of metals increase (Cs most reactive metal) while non-metal reactivity falls (F most reactive non-metal). The diagonal staircase separates metals, metalloids and non-metals.
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