Class 11 Chemistry
Chapter 3: Classification of Elements and Periodicity in Properties
Complete Question Bank
A. Multiple Choice Questions (MCQs)
1. The first scientist to classify elements into groups of three was:
A. Newlands
B. Mendeleev
C. Dobereiner
D. Moseley
Answer: C. Dobereiner
2. Dobereiner arranged elements according to:
A. Atomic number
B. Atomic mass
C. Number of electrons
D. Density
Answer: B. Atomic mass
3. In Dobereiner’s triads, the atomic mass of the middle element was approximately:
A. Double the first element
B. Half of the third element
C. Average of the other two elements
D. Equal to the first element
Answer: C
4. Newlands proposed:
A. Law of Octaves
B. Modern Periodic Law
C. Law of Triads
D. Atomic Theory
Answer: A
5. Newlands’ Law of Octaves was successful up to:
A. Hydrogen
B. Calcium
C. Iron
D. Uranium
Answer: B
6. Mendeleev arranged elements according to:
A. Atomic number
B. Atomic mass
C. Density
D. Valency only
Answer: B
7. Modern Periodic Law was proposed after the discovery of:
A. Electron
B. Proton
C. Neutron
D. Atomic number relationship
Answer: D
8. The scientist who proved atomic number is the fundamental property of an element was:
A. Rutherford
B. Moseley
C. Bohr
D. Dalton
Answer: B
9. Modern Periodic Law states that properties of elements are periodic functions of:
A. Atomic mass
B. Atomic volume
C. Atomic number
D. Density
Answer: C
10. The number of groups in the modern periodic table is:
A. 7
B. 8
C. 18
D. 32
Answer: C
B. Electronic Configuration Based MCQs
11. The element with configuration ns¹ belongs to:
A. Group 1
B. Group 2
C. Group 17
D. Group 18
Answer: A
12. The general electronic configuration of p-block elements is:
A. ns¹
B. ns²
C. ns²np¹⁻⁶
D. (n−1)d¹⁻¹⁰ns²
Answer: C
13. Transition elements belong to:
A. s-block
B. p-block
C. d-block
D. f-block
Answer: C
14. Lanthanoids belong to:
A. s-block
B. p-block
C. d-block
D. f-block
Answer: D
15. The last electron enters the f-orbital in:
A. p-block elements
B. f-block elements
C. s-block elements
D. noble gases
Answer: B
C. Periodic Trend MCQs
16. Atomic radius generally decreases from left to right because:
A. Atomic mass decreases
B. Nuclear charge increases
C. Number of shells decreases
D. Electrons disappear
Answer: B
17. Atomic radius increases down a group because:
A. Nuclear charge decreases
B. New shells are added
C. Electrons are removed
D. Valency decreases
Answer: B
18. The largest atom among Li, Na, K and Rb is:
A. Li
B. Na
C. K
D. Rb
Answer: D
19. Ionization enthalpy is highest for:
A. Alkali metals
B. Noble gases
C. Halogens
D. Transition metals
Answer: B
20. Ionization enthalpy decreases down the group due to:
A. Smaller size
B. Lower shielding
C. Increased atomic size
D. Higher attraction
Answer: C
D. Electron Gain Enthalpy MCQs
21. Most negative electron gain enthalpy is shown by:
A. Fluorine
B. Chlorine
C. Oxygen
D. Nitrogen
Answer: B
22. Noble gases have:
A. Highly negative electron gain enthalpy
B. Zero electron gain enthalpy
C. Positive electron gain enthalpy
D. Very low ionization energy
Answer: C
E. Electronegativity MCQs
23. Most electronegative element is:
A. Oxygen
B. Nitrogen
C. Fluorine
D. Chlorine
Answer: C
24. Electronegativity decreases down the group because:
A. Atomic size decreases
B. Atomic size increases
C. Nuclear charge disappears
D. Electrons decrease
Answer: B
F. Assertion–Reason Questions
Choose:
A. Both Assertion and Reason are true and Reason explains Assertion
B. Both true but Reason does not explain Assertion
C. Assertion true, Reason false
D. Assertion false, Reason true
1.
Assertion:
Atomic radius decreases across a period.
Reason:
Effective nuclear charge increases across a period.
Answer: A
2.
Assertion:
Noble gases have very high ionization enthalpy.
Reason:
They have completely filled valence shells.
Answer: A
3.
Assertion:
Cations are smaller than their parent atoms.
Reason:
Cations lose electrons.
Answer: A
4.
Assertion:
Metallic character increases down a group.
Reason:
Atomic size increases down the group.
Answer: A
G. Fill in the Blanks
- The modern periodic table is based on ______.
Answer: Atomic number
- The scientist who proposed Modern Periodic Law was ______.
Answer: Henry Moseley
- There are ______ groups in the periodic table.
Answer: 18
- There are ______ periods in the periodic table.
Answer: 7
- Elements of group 17 are called ______.
Answer: Halogens
- Group 18 elements are called ______.
Answer: Noble gases
- Elements of group 1 have ______ valence electron.
Answer: One
- Transition elements belong to ______ block.
Answer: d
- Lanthanoids and actinoids belong to ______ block.
Answer: f
- The most electronegative element is ______.
Answer: Fluorine
H. True or False
- Mendeleev arranged elements according to atomic number.
False
- Modern periodic table has 18 groups.
True
- Atomic radius increases across a period.
False
- Noble gases are chemically stable.
True
- Halogens belong to group 17.
True
- Metals are generally found on the right side of the periodic table.
False
- f-block elements are called inner transition elements.
True
- Ionization energy is always negative.
False
I. Match the Following
| Column A | Column B |
|---|---|
| Dobereiner | Triads |
| Newlands | Octaves |
| Mendeleev | Atomic mass |
| Moseley | Atomic number |
J. Very Short Answer Questions
1. What is periodicity?
Answer: Repetition of similar properties at regular intervals when elements are arranged in increasing atomic number.
2. What is atomic radius?
Answer: Distance between nucleus and outermost electron shell.
3. Define ionization enthalpy.
Answer: Energy required to remove an electron from a gaseous atom.
4. Define electronegativity.
Answer: Ability of an atom to attract shared electrons.
5. Name the most reactive non-metal.
Answer: Fluorine
K. Short Answer Questions
1. Write two limitations of Mendeleev’s periodic table.
Answer:
- Position of isotopes was not explained.
- Hydrogen position was uncertain.
2. Why does atomic radius decrease across a period?
Answer:
Because nuclear charge increases while electrons enter the same shell, causing stronger attraction.
3. Why are noble gases chemically inactive?
Answer:
They have completely filled valence shells and stable electronic configurations.
4. Why does metallic character increase down a group?
Answer:
Atomic size increases, making loss of electrons easier.
L. Long Answer Questions
1. Explain the development of the periodic table.
Points:
- Dobereiner triads
- Newlands octaves
- Mendeleev periodic table
- Moseley’s atomic number concept
- Modern periodic table
2. Explain periodic trends of atomic radius.
Include:
- Across period decrease
- Down group increase
- Role of nuclear charge and shielding effect
3. Explain s, p, d and f blocks.
Include:
- Position
- Electronic configuration
- Properties
- Examples
M. Numerical/Practice Problems
1. Arrange in increasing atomic size:
Li, Na, K, Rb
Answer:
Li < Na < K < Rb
2. Arrange in increasing metallic character:
P, Si, Mg, Na
Answer:
P < Si < Mg < Na
3. Arrange in increasing electronegativity:
Na, Mg, Al, Cl
Answer:
Na < Mg < Al < Cl
4. Which is larger?
Na or Na⁺
Answer:
Na
5. Which has higher ionization enthalpy?
Mg or Na
Answer:
Mg