Question

Which of the following statement is incorrect ?

• A. The atomic radius of Na is greater than that of Mg.
• B. Metallic bond in Mg is stronger than the metallic bond in Na.
• C. Melting and boiling points of Mg are greater than those of Ca.
• D. Mg and Ca both impart characteristic colour to the flame.

Answer 1

Answer: (D)

Mg and Ca both impart characteristic colour to the flame.

Answer 2

(1) Along the period, the nuclear charge increases and, therefore, atomic size decreases. So Na has larger atomic radius than Mg.

(2) Mg is smaller than Na and Mg has two valence electrons per atom while Na has only one valence electron per atom. So Mg has stronger metallic bond than that of Na (Na is a soft metal).

(3) Because of stronger metallic bond in Mg than Ca, boiling and melting points of Mg are greater than Ca.

(4) Mg does not impart characteristic colour to the flame because the electrons in Mg are too strongly bound to get excited by flame. Ca imparts brick red colour to the flame because of its low ionisation enthalpy.