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CodeVID-C11-03-CH-01
Classification of Elements and Periodicity in Properties — Full Chapter 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 given; for full solutions, raise doubts with your teacher.
Section A — Multiple Choice Questions
6 × 1 = 6 marks
1.
The Modern Periodic Law was given by:
- A.Mendeleev
- B.Newlands
- C.Moseley
- D.Dalton
2.
The element with $Z=12$ belongs to the:
- A.s-block
- B.p-block
- C.d-block
- D.f-block
3.
Most negative electron gain enthalpy is shown by:
- A.F
- B.Cl
- C.O
- D.N
4.
Number of groups in the long form table:
- A.8
- B.16
- C.18
- D.32
5.
Amphoteric oxide among the following:
- A.$\text{Na}_2\text{O}$
- B.$\text{Al}_2\text{O}_3$
- C.$\text{SO}_3$
- D.$\text{MgO}$
6.
Smallest isoelectronic species among $\text{O}^{2-}, \text{F}^-, \text{Na}^+, \text{Mg}^{2+}$:
- A.$\text{O}^{2-}$
- B.$\text{F}^-$
- C.$\text{Na}^+$
- D.$\text{Mg}^{2+}$
Section B — Short Answer (2 marks)
4 × 2 = 8 marks
7.
State the Modern Periodic Law and the cause of periodicity.
8.
Why is $\Delta_i H_1$ of B less than that of Be?
9.
Give the IUPAC name and symbol for $Z=109$.
10.
Arrange Li, Na, K, Cs in increasing ionisation enthalpy.
Section C — Long Answer (3 marks)
2 × 3 = 6 marks
11.
Explain the variation of atomic radius across a period and down a group.
12.
Why is the electron gain enthalpy of chlorine more negative than that of fluorine?
Section D — Detailed Answer (5 marks)
2 × 5 = 10 marks
13.
Describe the four blocks of the periodic table with general valence configurations and one example each, and state how the block is decided.
14.
Discuss periodic trends in metallic character and the nature of oxides across period 3, with examples.
Answer Key
Section A — Multiple Choice Questions
- (C) Moseley
- (A) s-block
- (B) Cl
- (C) 18
- (B) $\text{Al}_2\text{O}_3$
- (D) $\text{Mg}^{2+}$
Section B — Short Answer (2 marks)
- Properties are a periodic function of atomic number; periodicity arises from recurring valence-shell configurations.
- B's loosely held $2p^1$ electron is easier to remove than an electron from Be's stable filled $2s^2$.
- Unnilennium, symbol Une (later meitnerium).
- Cs < K < Na < Li (IE decreases down the group).
Section C — Long Answer (3 marks)
- Across a period radius decreases (rising $Z_{eff}$, same shell); down a group it increases (new shells added with greater shielding).
- F's small compact $2p$ shell causes strong electron repulsion on adding an electron, so less energy is released than for the larger Cl atom.
Section D — Detailed Answer (5 marks)
- s ($ns^{1-2}$, e.g. Na), p ($ns^2np^{1-6}$, e.g. Cl), d ($(n-1)d^{1-10}ns^{0-2}$, e.g. Fe), f ($(n-2)f^{1-14}$, e.g. Ce). The block is fixed by the subshell receiving the last electron.
- Metallic character decreases Na to Cl; oxides change from basic ($\text{Na}_2\text{O}, \text{MgO}$) through amphoteric ($\text{Al}_2\text{O}_3$) to acidic ($\text{P}_4\text{O}_{10}, \text{SO}_3, \text{Cl}_2\text{O}_7$), mirroring the fall in metallic character.
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