Chapter Exam

Chapter 3: Periodic Classification Of Elements — Online MCQ Test

Q: Which scientist proposed the Law of Triads?

Answer: A. Dobereiner — Johann Wolfgang Dobereiner observed that in groups of three elements (triads), the atomic weight of the middle element was approximately the average of the other two.

Q: What is the general electronic configuration of d-block elements?

Answer: A. (n-1)d^1-10 ns^0-2 — The d-block elements involve the filling of inner d-orbitals, represented by the configuration (n-1)d^1-10 ns^0-2.

Q: Which periodic property decreases from left to right across a period?

Answer: C. Atomic radius — As effective nuclear charge increases across a period, the electrons are pulled closer to the nucleus, decreasing the atomic radius.

Q: Which element has an anomalous electronic configuration involving a shift from the 4s orbital to the 3d orbital to achieve half-filled stability?

Answer: B. Chromium — Chromium (Z=24) has the configuration [Ar] 3d5 4s1 to gain the extra stability of a half-filled d-subshell.

CHEMISTRY · CLASS 11th · Tamil Nadu State Board

Practice Chapter 3: Periodic Classification Of Elements with a free chapter-wise online MCQ test for Tamil Nadu State Board CLASS 11th CHEMISTRY. This chapter covers: This chapter covers periodic table development modern periodic law and periodic property trends. Students study atomic radii ionic radii ionization energy electron affinity electro.... AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 3: Periodic Classification Of Elements — Important Questions & Answers (FAQ)

Frequently asked questions from Tamil Nadu State Board CLASS 11th CHEMISTRY — Chapter 3: Periodic Classification Of Elements, with answers and explanations. These are sample questions; the exam has its own separate question set.

Which scientist proposed the Law of Triads?

A. Dobereiner ✓
B. Newlands
C. Mendeleev
D. Lothar Meyer

Answer: A. Dobereiner
Johann Wolfgang Dobereiner observed that in groups of three elements (triads), the atomic weight of the middle element was approximately the average of the other two.

What is the general electronic configuration of d-block elements?

A. (n-1)d^1-10 ns^0-2 ✓
B. ns^1-2
C. (n-1)d^1-10 ns^2
D. ns^2 np^1-6

Answer: A. (n-1)d^1-10 ns^0-2
The d-block elements involve the filling of inner d-orbitals, represented by the configuration (n-1)d^1-10 ns^0-2.

Which periodic property decreases from left to right across a period?

A. Ionization energy
B. Electronegativity
C. Atomic radius ✓
D. Electron affinity

Answer: C. Atomic radius
As effective nuclear charge increases across a period, the electrons are pulled closer to the nucleus, decreasing the atomic radius.

Why is the electron gain enthalpy of Chlorine more negative than that of Fluorine?

A. Chlorine is more electronegative
B. Fluorine has a smaller size causing inter-electronic repulsion ✓
C. Chlorine has a higher atomic mass
D. Fluorine is a gas

Answer: B. Fluorine has a smaller size causing inter-electronic repulsion
Due to the small size of the fluorine atom, the incoming electron experiences repulsion from existing electrons, making the process less exothermic compared to Chlorine.

Which element has an anomalous electronic configuration involving a shift from the 4s orbital to the 3d orbital to achieve half-filled stability?