Unit 9: Classification of Elements and Periodicity in Properties — Online MCQ Test
CHEMISTRY · NEET (All) · NEET
Practice Unit 9: Classification of Elements and Periodicity in Properties with a free chapter-wise online MCQ test.
This chapter covers: Modem periodic law and present form of the periodic table s p. d and f block elements periodic trends in properties of elements atomic and ionic radii ionization enthalpy electron....
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Unit 9: Classification of Elements and Periodicity in Properties — Important Questions & Answers
Which among the following electronic configurations belong to main group elements? A. [Ne]3s¹ B. [Ar]3d³4s² C. [Kr]4d¹⁰5s²5p⁵ D. [Ar]3d¹⁰4s¹ E. [Rn]5f⁰6d²7s²
- A. B and E only
- B. A and C only
- C. D and E only
- D. A, C and D only
Answer: B. A and C only
Main group elements have s or p orbitals as the valence shell (s-block and p-block). A ([Ne]3s¹) and C ([Kr]4d¹⁰5s²5p⁵) are main group elements. B, D, and E are transition or inner-transition metals.
Main group elements have s or p orbitals as the valence shell (s-block and p-block). A ([Ne]3s¹) and C ([Kr]4d¹⁰5s²5p⁵) are main group elements. B, D, and E are transition or inner-transition metals.
In which of the following options the order of arrangement does not agree with the variation of property indicated against it?
- A. B < C < N < O (increasing first ionisation enthalpy)
- B. I < Br < Cl < F (increasing electron gain enthalpy)
- C. Li < Na < K < Rb (increasing metallic radius)
- D. Al3+ < Mg2+ < Na+ < F- (increasing ionic size)
Answer: A. B < C < N < O (increasing first ionisation enthalpy)
First IE of Nitrogen is higher than Oxygen due to stable half-filled 2p subshell (2p3). Electron gain enthalpy of Fluorine is less negative than Chlorine due to small size and inter-electronic repulsion. Both A and B are technically incorrect statements.
First IE of Nitrogen is higher than Oxygen due to stable half-filled 2p subshell (2p3). Electron gain enthalpy of Fluorine is less negative than Chlorine due to small size and inter-electronic repulsion. Both A and B are technically incorrect statements.
Which one of the following orders in correct for the bond dissociation enthalpy of halogen molecules?
- A. Cl2 > Br2 > F2 > I2
- B. Br2 > I2 > F2 > Cl2
- C. F2 > Cl2 > Br2 > I2
- D. I2 > Br2 > Cl2 > F2
Answer: A. Cl2 > Br2 > F2 > I2
Due to the small size of the fluorine atom, the lone pairs have significant inter-electronic repulsion, weakening the F-F bond. Thus, Cl2 has the highest bond dissociation enthalpy.
Due to the small size of the fluorine atom, the lone pairs have significant inter-electronic repulsion, weakening the F-F bond. Thus, Cl2 has the highest bond dissociation enthalpy.
Which one of the following orders is correct for the bond dissociation enthalpy of halogen molecules ?
- A. Cl2 > Br2 > F2 > I2
- B. Br2 > I2 > F2 > Cl2
- C. F2 > Cl2 > Br2 > I2
- D. I2 > Br2 > Cl2 > F2
Answer: A. Cl2 > Br2 > F2 > I2
The bond dissociation enthalpy of F2 is lower than that of Cl2 and Br2 due to the small size of the fluorine atom, which leads to strong inter-electronic repulsion between the lone pairs.
The bond dissociation enthalpy of F2 is lower than that of Cl2 and Br2 due to the small size of the fluorine atom, which leads to strong inter-electronic repulsion between the lone pairs.
Magnesium reacts with an element (X) to form an ionic compound. If the ground state electronic configuration of (X) is 1s² 2s² 2p³, the simplest formula for this compound is
- A. Mg₂X₃
- B. Mg₃X₂
- C. Mg₂X
- D. MgX₂
Answer: B. Mg₃X₂
Element X with configuration 1s² 2s² 2p³ is nitrogen (N), which has 5 valence electrons and forms X³⁻ ion (gaining 3 electrons to complete octet). Magnesium forms Mg²⁺ ion. To balance charges: 3 Mg²⁺ provides +6 charge; 2 N³⁻ provides −6 charge. So the formula is Mg₃X₂ (analogous to Mg₃N₂).
Element X with configuration 1s² 2s² 2p³ is nitrogen (N), which has 5 valence electrons and forms X³⁻ ion (gaining 3 electrons to complete octet). Magnesium forms Mg²⁺ ion. To balance charges: 3 Mg²⁺ provides +6 charge; 2 N³⁻ provides −6 charge. So the formula is Mg₃X₂ (analogous to Mg₃N₂).