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Periodic Table and Periodicity question

2025 · 29 Jan · Shift 1 · Q19
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Periodic Table and Periodicity question

2025 · 29 Jan · Shift 1 · Q19

JEE MainChemistryPeriodic Table and PeriodicityMCQ+4 / −1
An element ‘E’ has the ionisation enthalpy value of 374 kJ mol⁻¹. ‘E’ reacts with elements A, B, C and D with electron gain enthalpy values of −328, −349, −325 and −295 kJ mol⁻¹, respectively. The correct order of the products EA, EB, EC and ED in terms of ionic character is :
  1. A
    EB > EA > EC > ED
  2. B
    EA > EB > EC > ED
  3. C
    ED > EC > EA > EB
  4. D
    ED > EC > EB > EA
View written solutionFree

Correct answer: A

  1. Identify element EEE from ionisation enthalpy

The given ionisation enthalpy of EEE is 374 kJ mol−1374\ \text{kJ mol}^{-1}374 kJ mol−1, which is very low and corresponds to an alkali metal. This value is closest to potassium (K).

So, compounds EA,EB,EC,EDEA, EB, EC, EDEA,EB,EC,ED are essentially ionic compounds of an alkali metal with different anions.


  1. Use Fajan's rule / electronegativity tendency

Since the cation is the same in all four compounds (E+E^+E+), the ionic character mainly depends on the nature of the anion.

Greater tendency to gain electron (more negative electron gain enthalpy) means the element is more non-metallic and forms a more ionic bond with an alkali metal.

Given electron gain enthalpies:

  • A=−328 kJ mol−1A = -328\ \text{kJ mol}^{-1}A=−328 kJ mol−1
  • B=−349 kJ mol−1B = -349\ \text{kJ mol}^{-1}B=−349 kJ mol−1
  • C=−325 kJ mol−1C = -325\ \text{kJ mol}^{-1}C=−325 kJ mol−1
  • D=−295 kJ mol−1D = -295\ \text{kJ mol}^{-1}D=−295 kJ mol−1

More negative value ⇒\Rightarrow⇒ greater electron-accepting tendency ⇒\Rightarrow⇒ more ionic compound with EEE.

Thus the order of ionic character follows:

B>A>C>DB > A > C > DB>A>C>D

Hence,

EB>EA>EC>EDEB > EA > EC > EDEB>EA>EC>ED
  1. Check options
  • A: EB>EA>EC>EDEB > EA > EC > EDEB>EA>EC>ED ✅
  • B: EA>EB>EC>EDEA > EB > EC > EDEA>EB>EC>ED ❌
  • C: ED>EC>EA>EBED > EC > EA > EBED>EC>EA>EB ❌
  • D: ED>EC>EB>EAED > EC > EB > EAED>EC>EB>EA ❌

  1. Final Answer

The correct order is:

EB>EA>EC>ED\boxed{EB > EA > EC > ED}EB>EA>EC>ED​

So, Option A is correct.

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