Chemistry Chapter 3: Classification of Elements (50 Full MCQs)
1. The IUPAC name of element with atomic number 119 is:
A. Ununennium
B. Unbinilium
C. Ununnilium
D. Ununseptium
Answer: A
Solution: For 119: 1=un, 1=un, 9=enn. Name: Ununennium. Symbol: Uue.
2. Maximum number of elements in the 6th period is:
A. 18
B. 32
C. 8
D. 50
Answer: B
Solution: 6th period includes 6s, 4f, 5d, and 6p orbitals (2+14+10+6 = 32 elements).
3. Which block contains metals, non-metals, and metalloids?
A. s-block
B. p-block
C. d-block
D. f-block
Answer: B
Solution: The p-block is the only block containing all three types of elements.
4. The element with Z=114 belongs to:
A. Group 14, Period 7
B. Group 16, Period 7
C. Group 14, Period 6
D. Group 13, Period 7
Answer: A
Solution: It follows Lead (Z=82) in Group 14 (Carbon family).
5. General configuration of f-block elements is:
A. (n-2)f1-14(n-1)d0-1ns2
B. (n-1)f1-14nd0-1ns2
C. (n-2)f0-14(n-1)d10ns2
D. nf1-14(n-1)d1ns2
Answer: A
Solution: Electrons fill the (n-2)f subshell.
6. Total number of elements in s-block is:
A. 12
B. 14
C. 10
D. 13
Answer: B
Solution: 2 from Group 1, 2 from Group 2 across 7 periods, but only 14 total (including H and He).
7. Screening effect order for the same shell is:
A. s > p > d > f
B. f > d > p > s
C. s = p = d = f
D. p > s > d > f
Answer: A
Solution: s-orbitals are closer to the nucleus and provide better shielding.
8. Element with Z=33 belongs to:
A. Period 3
B. Period 4
C. Group 13
D. Group 17
Answer: B
Solution: Configuration: [Ar] 3d10 4s2 4p3. Highest n=4, so Period 4.
9. Which group contains only metals?
A. Group 1
B. Group 2
C. Group 17
D. Group 18
Answer: B
Solution: Group 1 contains Hydrogen (non-metal), while Group 2 contains only metals.
10. First noble gas is:
A. Neon
B. Helium
C. Argon
D. Radon
Answer: B
Solution: Helium (Z=2) is the first noble gas in Period 1.
11. Largest ionic radius among isoelectronic species O2-, F-, Na+, Mg2+ is:
A. Mg2+
B. Na+
C. F-
D. O2-
Answer: D
Solution: Size increases as nuclear charge (Z) decreases in isoelectronic species. O2- has Z=8.
12. Atomic radius of Gallium (Ga) is less than Aluminum (Al) due to:
A. Lanthanide contraction
B. Poor shielding by 3d electrons
C. Inert pair effect
D. Large size
Answer: B
Solution: 3d electrons shield poorly, increasing Zeff and shrinking the atom.
13. Across a period, atomic size decreases due to:
A. Decrease in Zeff
B. Increase in Zeff
C. Increase in shielding
D. Addition of shells
Answer: B
Solution: Effective nuclear charge increases while electrons are added to the same shell.
14. Which is the correct size order?
A. I- > I > I+
B. I+ > I > I-
C. I > I- > I+
D. I- > I+ > I
Answer: A
Solution: Anion > Parent Atom > Cation.
15. Lanthanide contraction is caused by:
A. 4f electrons
B. Poor shielding of 4f electrons
C. 5d electrons
D. 6s electrons
Answer: B
Solution: Poor shielding of 4f electrons causes the nucleus to pull 6s electrons more strongly.
16. van der Waals radius is ______ than covalent radius.
A. Smaller
B. Larger
C. Equal
D. Half
Answer: B
Solution: van der Waals radius accounts for non-bonding distance between atoms.
17. Which gas has the largest atomic radius in Period 2?
A. Lithium
B. Fluorine
C. Neon
D. Oxygen
Answer: C
Solution: Noble gases are measured by van der Waals radius, which is much larger than covalent radii.
18. Radius of Fe2+ is ______ than Fe3+.
A. Larger
B. Smaller
C. Same
D. Triple
Answer: A
Solution: Higher positive charge leads to greater contraction of the electron cloud.
19. Atomic radius increases down a group due to:
A. Increase in Zeff
B. Addition of new shell
C. Decrease in Z
D. Shielding effect
Answer: B
Solution: Adding a principal energy level outweighs the increase in nuclear charge.
20. Zr and Hf have similar radii due to:
A. Being in same group
B. Lanthanide contraction
C. Same Z
D. Shielding
Answer: B
Solution: Contraction in the 5d series (Hf) cancels out the expected size increase from Zr.
21. 1st Ionization Enthalpy is highest for:
A. B
B. C
C. N
D. O
Answer: C
Solution: Nitrogen has a stable half-filled 2p3 configuration.
22. Element with lowest 1st I.E. is:
A. Li
B. Cs
C. Fr
D. He
Answer: B
Solution: Cesium has the largest size and lowest effective nuclear pull on valence electrons.
23. Successive I.E. values are always:
A. I.E.1 > I.E.2
B. I.E.2 > I.E.1
C. I.E.1 = I.E.2
D. Random
Answer: B
Solution: Removing an electron from a positive ion is always harder due to increased Z/e ratio.
24. Be has higher I.E. than B due to:
A. Penetration effect of 2s
B. Size
C. Nuclear charge
D. Shielding
Answer: A
Solution: 2s electrons of Be are more penetrated towards the nucleus than 2p of B.
25. Noble gases have very high I.E. because:
A. Stable octet
B. Small size
C. High Zeff
D. All of these
Answer: D
Solution: Full shells and high Zeff make electron removal extremely difficult.
26. Order of 1st I.E. in Group 13:
A. B > Al > Ga > In > Tl
B. B > Tl > Ga > Al > In
C. B > Ga > Al > Tl > In
D. Al > B > Ga
Answer: B
Solution: Irregular trend due to d-block and f-block contractions.
27. Which ion is isoelectronic with Neon?
A. O-
B. Mg2+
C. Cl-
D. K+
Answer: B
Solution: Mg2+ has 10 electrons, same as Ne.
28. I.E. decreases down the group due to:
A. Size increase
B. Shielding increase
C. Both A and B
D. Z increase
Answer: C
Solution: Larger distance and more inner shells reduce the nuclear pull.
29. Highest second I.E. is of:
A. Na
B. Mg
C. Al
D. Si
Answer: A
Solution: Removing 2nd electron from Na+ involves breaking a stable noble gas core (2p6).
30. Metallic character is highest for:
A. s-block
B. p-block
C. d-block
D. f-block
Answer: A
Solution: Low I.E. allows s-block elements to lose electrons easily.
31. Most negative electron gain enthalpy is of:
A. F
B. Cl
C. Br
D. I
Answer: B
Solution: F is too small, causing interelectronic repulsion for the incoming electron.
32. Most electronegative element is:
A. O
B. F
C. Cl
D. N
Answer: B
Solution: Fluorine has the highest tendency to attract shared electrons (Pauling scale = 4.0).
33. Noble gases have ______ electron gain enthalpy.
A. Highly negative
B. Positive
C. Zero
D. Negative
Answer: B
Solution: Energy must be supplied to force an electron into a higher shell of a stable atom.
34. Electronegativity increases across a period because:
A. Size increases
B. Zeff increases
C. Shielding increases
D. I.E. decreases
Answer: B
Solution: Stronger nuclear pull attracts bonding electrons more effectively.
35. Order of electronegativity:
A. F > O > N
B. N > O > F
C. O > F > N
D. F > N > O
Answer: A
Solution: Values are roughly F(4.0) > O(3.5) > N(3.0).
36. Pauling scale is based on:
A. Bond energies
B. I.E. and E.A.
C. Atomic size
D. Metallic character
Answer: A
Solution: It relates electronegativity to the extra stability of polar bonds.
37. Element with highest electron affinity:
A. Cl
B. F
C. O
D. S
Answer: A
Solution: Chlorine releases the most energy when accepting an electron.
38. Across a period, non-metallic character:
A. Increases
B. Decreases
C. Constant
D. First increases
Answer: A
Solution: Higher I.E. and EN favor non-metallic behavior.
39. Which is most electropositive?
A. Li
B. Na
C. K
D. Cs
Answer: D
Solution: Cesium loses its valence electron most easily.
40. Nature of oxides changes from left to right as:
A. Acidic to Basic
B. Basic to Acidic
C. Basic to Neutral
D. Neutral to Basic
Answer: B
Solution: Metals form basic oxides; non-metals form acidic oxides.
41. Diagonal relationship is between:
A. Li-Mg
B. Be-Al
C. B-Si
D. All of these
Answer: D
Solution: Diagonal elements share similar charge/radius ratios.
42. Amphoteric oxide is:
A. Na2O
B. Al2O3
C. CO2
D. SO2
Answer: B
Solution: Aluminum oxide reacts with both acids and bases.
43. Strongest reducing agent in aqueous solution is:
A. Li
B. Na
C. K
D. Cs
Answer: A
Solution: Lithium has the highest hydration enthalpy due to small size.
44. Strongest oxidizing agent is:
A. F2
B. Cl2
C. I2
D. O2
Answer: A
Solution: Fluorine has the highest reduction potential.
45. Liquid non-metal is:
A. Hg
B. Br2
C. Ga
D. S
Answer: B
Solution: Bromine is the only non-metal that is liquid at STP.
46. Most basic hydroxide:
A. NaOH
B. KOH
C. CsOH
D. LiOH
Answer: C
Solution: Basic strength of Group 1 hydroxides increases down the group.
47. Inert pair effect is most prominent in:
A. C
B. Si
C. Ge
D. Pb
Answer: D
Solution: s-electrons of the valence shell become reluctant to bond in heavier p-block elements.
48. Typical elements are:
A. Period 2
B. Period 3
C. Period 4
D. Period 1
Answer: B
Solution: Period 3 elements represent the properties of their respective groups.
49. Nature of Cl2O7:
A. Strongly acidic
B. Strongly basic
C. Amphoteric
D. Neutral
Answer: A
Solution: It reacts with water to form Perchloric acid (HClO4), the strongest mineral acid.
50. Triad system was given by:
A. Mendeleev
B. Dobereiner
C. Newlands
D. Moseley
Answer: B
Solution: Johann Dobereiner arranged elements in groups of three with similar properties.
