The s-Block Elements

Question 153
CBSEENCH11007131

The alkaline earth metals are denser and harder than the corresponding alkali metals. Explain ?

Solution

The atoms of alkaline earth elements have smaller size and stronger intermetallic bonds, as compared to alkali metals. Therefore, they are more closely packed in their crystal lattices which account for high density and hardness of these elements.
In general, the density first decreases up to calcium and then increases up to radium. The case for a decrease in density up to calcium is presumably due to less good packing arrangement of constituents in the solid lattice.

Question 154
CBSEENCH11007132

What is the trend of atomic and ionic radii of alkaline earth metals within the group?

Solution

Within the group, the atomic as well as ionic radii increase in going from beryllium (Be) to radium (Ra). This is due to the addition of new shells, the effect of which is more predominate than the increase in nuclear charge.

Question 155
CBSEENCH11007133

The atomic and ionic radii of alkaline earth metals are smaller than those of the corresponding alkali metals. Explain.

Solution

The atoms of alkaline earth metals have a higher nuclear charge due to which the electron cloud is pulled towards the nucleus. This causes a decrease in the atomic and ionic radii of alkaline earth metals.

Question 156
CBSEENCH11007134

How will you explain that alkaline earth metals have much higher melting and boiling points than those of alkali metals?

 

Solution
Atoms or ions of alkaline earth metals are smaller than the corresponding alkali metals. Because of their smaller size and a more closed packed structure, alkaline earth metals have higher melting and boiling points than the alkali metals.

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