The property/properties that show irregularity in first four elements of group-17 is/are : (A) Covalent radius (B) Electron affinity (C) Ionic radius (D) First ionization energy Choose the correct answer from the options given below:

Solution & Explanation

### Related Formula Standard downward group variations typically follow predictable monotonic pathways: textRadius propto textNumber of shells textIonization Energy propto frac1textAtomic Size ### Core Logic Let's review the explicit values and trends across mathrmF, Cl, Br, I: * **Covalent radius**: mathrmF < Cl < Br < I (Perfect monotonic increase). * **Ionic radius**: mathrmF^- < Cl^- < Br^- < I^- (Perfect monotonic increase). * **First ionization energy**: mathrmF > Cl > Br > I (Perfect monotonic decrease). * **Electron affinity**: mathrmCl > F > Br > I (Irregular trend! Fluorine has an anomalously lower electron affinity than Chlorine due to high inter-electronic repulsions inside its exceptionally compact 2p valence subshell). ### Step 1: Conclusion Therefore, only electron affinity (B) demonstrates an irregular trend line among the first four halogens. ### Pattern Recognition Fluorine anomalous properties are a classic JEE question archetype. Whenever a question asks about irregularities in halogens, immediately check Electron Gain Enthalpy (Electron Affinity) and Bond Dissociation Enthalpy, where Fluorine routinely breaks the monotonic descending order. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Classification of Elements and Periodicity in Properties Class 12 Chemistry: The p-Block Elements

Reference Study Guides

Classification Of Elements And Periodicity In Properties

More Classification of Elements and Periodicity in Properties Previous-Year Questions — Page 6

Q84 jee_main_2024_30_jan_morning IUPAC Nomenclature for Elements > 100
If IUPAC name of an element is "Unununnium" then the element belongs to nth group of periodic table. The value of n is
Numerical Answer. Answer: 11 to 11

Solution

### Core Logic Decode the IUPAC name "Unununnium" into its atomic number. Un = 1 Un = 1 Un = 1 Suffix = ium So, the atomic number is 111. ### Step 1: Finding group number For d-block elements with Z > 100, the group number is the last two digits of the atomic number. Since Z = 111, the element belongs to group 11 (the Copper group). ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Classification of Elements and Periodicity in Properties
Q80 jee_main_2024_31_jan_evening Periodic Trends in Properties
Consider the following elements.
Group downarrowA^primeB^prime rightarrow Period
C^primeD^prime
Which of the following is/are true about A^prime, B^prime, C^prime and D^prime? A. Order of atomic radii: B^prime < A^prime < D^prime < C^prime B. Order of metallic character: B^prime < A^prime < D^prime < C^prime C. Size of the element: D^prime < C^prime < B^prime < A^prime D. Order of ionic radii: B^prime + < A^prime + < D^prime + < C^prime + Choose the correct answer from the options given below:
  • A. text1. A only
  • B. text2. A, B and D only
  • C. text3. A and B only
  • D. text4. B, C and D only

Solution

### Core Logic From the grid layout, A^prime and B^prime are in the same period (left to right), while C^prime and D^prime are below them in the next period. In general, moving along a period from left to right, size decreases and metallic character decreases. Moving down a group, size increases and metallic character increases. Atomic Radii / Size: B^prime < A^prime (across period) D^prime < C^prime (across period) A^prime < C^prime and B^prime < D^prime (down the group) Combining them: B^prime < A^prime < D^prime < C^prime. (Statement A is correct, C is incorrect). Metallic Character: B^prime < A^prime and D^prime < C^prime Overall trend follows size closely for these blocks: B^prime < A^prime < D^prime < C^prime. (Statement B is correct). Ionic Radii (+ ions): Follows the same basic trend as atomic radii: B^prime + < A^prime + < D^prime + < C^prime +. (Statement D is correct). ### Step 1: Final Selection Statements A, B, and D are correct. Statement C contradicts A, so it is incorrect. Option 2 is the right choice. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Classification of Elements and Periodicity in Properties
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 (Delta_egH) values are considered with their signs when ordering from largest to smallest algebraically.
ElementDelta_egH text (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. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Classification of Elements and Periodicity in Properties

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