Question

Which among the following statements is NOT true?

• A. Compounds of unipositive ions of alkali metals are paramagnetic.
• B. Alkali metals have low density.
• C. All alkali metals are silvery white and soft.
• D. Alkali metals are most electropositive elements.

Hint:

Remember that all stable ions of representative s-block elements (Group 1 and Group 2) always achieve noble gas configurations, meaning they have no unpaired electrons and are always colorless and diamagnetic!

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
We need to identify the false statement regarding the physical and chemical properties of alkali metals (Group 1 elements).

Step 2: Key Formula or Approach:
Alkali metals have a general valence electron configuration of $ns^1$. To determine magnetic properties, we look at the presence of unpaired electrons. Paramagnetic species have unpaired electrons, while diamagnetic species have only paired electrons.

Step 3: Detailed Explanation:
Let's evaluate the statements:
(B) True. Alkali metals have large atomic radii and weak metallic bonding, resulting in relatively low densities compared to other metals.
(C) True. They are typically silvery-white in appearance and soft enough to be cut with a knife.
(D) True. Because they only need to lose one electron to achieve a stable noble gas configuration, they have very low ionization energies and are highly electropositive.
(A) False. Neutral alkali metals have one unpaired electron ($ns^1$) and are paramagnetic. However, when they form unipositive ions ($M^+$), they lose this single valence electron. The resulting ion has a stable, fully paired noble gas electron configuration. Therefore, compounds of unipositive alkali metal ions are strictly diamagnetic, not paramagnetic.

Step 4: Final Answer:
The statement that unipositive ions of alkali metals are paramagnetic is NOT true, matching option (A).