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Classification of Elements and Periodicity in Properties appeared 36 times across 3 years — 4.2% of Chemistry. This question is from Metallic Character And Valence Electrons.

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Questions 9 16 11 36
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Consider the elements N, P, O, S, Cl and F. The number of valence electrons present in the elements with most and least metallic character from the above list is respectively.

Solution & Explanation

Core Logic

Metallic character decreases across a period and increases down a group. Among N, P, O, S, Cl and F: Least metallic element = F (Group 17, Period 2), valence electrons = 7. Most metallic element = P (Group 15, Period 3), valence electrons = 5.

Step 1: Final Conclusion

The number of valence electrons for most and least metallic elements are 5 and 7 respectively.

Pattern Recognition

F is the most electronegative (least metallic). P is the lowest and leftmost in this non-metal set (most metallic).

Chapter Mix

Class 11 Chemistry: Classification of Elements and Periodicity in Properties

Reference Study Guides

Classification Of Elements And Periodicity In Properties

More Classification Of Elements And Periodicity In Properties Previous-Year Questions — Page 8

Q70 jee_main_2024_31_jan_morning Electron Gain Enthalpy
The correct sequence of electron gain enthalpy of the elements listed below is A. Ar B. Br C. F D. S Choose the most appropriate from the options given below:
  • A. C > B > D > A
  • B. A > D > B > C
  • C. A > D > C > B
  • D. D > C > B > A

Solution

Core Logic

Electron gain enthalpy (ΔegH) values are considered with their signs when ordering from largest to smallest algebraically.

ElementΔegH (kJ/mol)
F-333
S-200
Br-325
Ar+96

Arranging these algebraically from highest to lowest: +96 > -200 > -325 > -333 Thus, Ar > S > Br > F, which corresponds to A > D > B > C.

Pattern Recognition

Noble gases always have positive electron gain enthalpies (highest algebraically). Halogens have highly negative values (lowest algebraically). Fluorine is highly negative, Bromine is slightly less negative. Sulfur sits in between.

Chapter Mix

Class 11 Chemistry: Classification of Elements and Periodicity in Properties

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