Identify the incorrect order corresponding the mentioned property.

Identify the incorrect order corresponding the mentioned property.
  1. $\mathrm{Al}_2 \mathrm{O}_3 < \mathrm{MgO} < \mathrm{Na}_2 \mathrm{O} < \mathrm{K}_2 \mathrm{O}$ : Basicity
  2. $\mathrm{NH}_3 < \mathrm{PH}_3 < \mathrm{AsH}_3:$ Acidity
  3. $\mathrm{Li}^{+} < \mathrm{Na}^{+} < \mathrm{K}^{+} < \mathrm{Cs}^{+}$: lonic radius
  4. $\mathrm{Li} < \mathrm{Be} < \mathrm{B} < \mathrm{C}$ : First ionisation enthalpy

Solution

The first ionisation energy generally increases as we move from left to right across a period. This is due to increasing nuclear charge which results in the strong attraction of outermost electron to the nucleus. So, the correct trend of first ionisation enthalpy is $\mathrm{Li} < \mathrm{Be} < \mathrm{B} < \mathrm{C}$

Asked in: AP EAMCET 2021 (24 Aug Shift 2)

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