Question

Which of the following statements is incorrect for the alkali metals ?
A. The metallic (or electropositive) character increases down the group.
B. When freshly out, they are silvery white and on exposure to air, they are tarnished (i.e., become dull).
C. They assume a face-centered cubic lattice structure.
D. They are soft and can be cut with a knife.

Answer 1

Correct Answer - C
At normal temperatures, all the alkali metals adopt a body-centered cubic type of lattice. However, at very low temperatures, Li forms a hexagonal close-packed structure with a coordination number of 12.
(1) As we move down the group, the tendency of the elements to lose electrons increases due to decrease of ionization enthalpy.
(2) Due to high reactivity, they are easily corroded.
(4) Metallic bonds in alkali metals are very weak because the atoms of alkali metals have bigger kernels and smaller number (just one) of valence electrons.