Question

Which of the following is the correct order with respect to the property indicated?

• A. \( \mathrm{Cl>F} \) (Ionisation energy)
• B. \( \mathrm{K_2O>Na_2O>Al_2O_3} \) (Basic nature)
• C. \( \mathrm{K>Na>Al>Mg} \) (Metallic character)
• D. None of these

Hint:

Periodic trends to remember: \begin{itemize} \item Ionisation energy increases across a period, decreases down a group \item Metallic character decreases across a period \item Basic nature of oxides decreases from left to right \end{itemize}

Answer 1

The Correct Option is B

Let's analyze each option given in the question based on their respective properties:

1. Ionisation Energy: \(\mathrm{Cl > F}\) 

Ionization energy is the energy required to remove an electron from a gaseous atom or ion. Generally, ionization energy increases across a period and decreases down a group in the periodic table. Between chlorine (\(\mathrm{Cl}\)) and fluorine (\(\mathrm{F}\)), fluorine has a higher ionization energy than chlorine. Therefore, the statement \(\mathrm{Cl > F}\) is incorrect.

1. Basic Nature: \(\mathrm{K_2O > Na_2O > Al_2O_3}\)

The basicity of oxides increases with the electropositivity of the metal. Potassium oxide (\(\mathrm{K_2O}\)) and sodium oxide (\(\mathrm{Na_2O}\)) are basic oxides, while aluminum oxide (\(\mathrm{Al_2O_3}\)) is amphoteric. Within basic oxides, \(\mathrm{K_2O}\) is more basic than \(\mathrm{Na_2O}\). Hence, this order is correct.

1. Metallic Character: \(\mathrm{K > Na > Al > Mg}\)

The metallic character is determined by the ease with which an element can lose electrons. It increases down a group and decreases across a period. Potassium (\(\mathrm{K}\)) and sodium (\(\mathrm{Na}\)) are in the same group, with potassium being more metallic. Aluminum (\(\mathrm{Al}\)) and magnesium (\(\mathrm{Mg}\)) are less metallic than potassium and sodium. However, magnesium is actually more metallic than aluminum. Therefore, this order is incorrect.

1. None of these

Based on the analysis above, the correct order for the property indicated is \(\mathrm{K_2O > Na_2O > Al_2O_3}\) with respect to basic nature.