Manipal MET2015ChemistryClassification of Elements and Periodicity in Properties
In which of the following arrangement the order is not according to the property indicated against it?
Options
- ALi Na K Rb (increasing metallic radius)
- B1 Br F Cl (increasing electron gain enthalpy, with negative sign)
- CB C N O (increasing . first ionisation enthalpy)
- DAl ³⁺ Mg ²⁺ Na ⁺ F ⁻ (increasing ionic size)
Correct answer
C. B C N O (increasing . first ionisation enthalpy)
Step-by-step solution
(a) Metallic radii increase in a group from top to bottom. Thus, Li Na K Rb is true. (b) Electron gain enthalpy of Cl F and afterwards it decreases along a group. (c) Ionisation enthalpy increase along a period left to right but due to presence of half-filled orbital in N , ionisation enthalpy of N O . Thus B C N O is incorrect. (d) For isoelectronic species, ionic size 1 atomic number Thus , Al ³⁺ Mg ²⁺ Na ⁺ F ⁻ is true.