S- And p-Block Elements Test - 2

Liquid sodium metal is used as a coolant in fast breeder nuclear reactors.
Metallic beryllium is used for making windows of X-ray tubes.
Cesium is used in devising photoelectric cells.
Radium salts are used in radiotherapy, for e.g., in the treatment of cancer.

In alkaline earth metal hydroxides, the anion being common, the cationic radius will influence the lattice enthalpy.

Compounds of alkaline earth metals are more extensively hydrated than those of alkali metals.
Aqueous solution of calcium hydroxide is known as slaked lime and when excess water is added, a suspension is formed which is known as the milk of lime or whitewash. On filtration, the filtrate (saturated solution) obtained is known as limewater.

Calcium and strontium crystallize in face centered cubic structure.

Yes, Beryllium and magnesium do not impart characteristic colour to oxidizing flame.

Francium is highly radioactive; its longest-lived isotope 223-Fr has a half-life of only 21 minutes.
The hydration enthalpies of alkaline earth metal ions are larger than those of alkali metal ions. Thus, compounds of alkaline earth metals are more extensively hydrated than those of alkali metals, e.g., MgCl₂ and CaCl₂ exist as MgCl₂.6H₂O and CaCl₂.6H₂O while NaCl and KCl do not form such hydrates.

Except BeO, which is amphoteric, all alkali metal and alkaline earth metal oxides are basic.

Li resembles Mg mainly due to similarity in sizes of their atoms and ions. The main points of similarity are:
1. Both Li and Mg are quite hard.

2. Both LiOH and Mg(OH)₂ are weak bases.
3. Carbonates of both Li and Mg, on heating, decompose to produce oxides and carbon dioxide.

4. Both Li and Mg react with nitrogen to give ionic nitrides.
5. Nitrates of both Li and Mg decompose on heating to give oxides.

6. Both Li and Mg do not form solid bicarbonates.
7. Because of covalent character, LiCl and MgCl₂ are soluble in ethanol.
8. The hydroxides, bicarbonates and fluorides of both Li and Mg are sparingly soluble in water.
 

Melting points of alkaline earth metals are greater than those of alkali metals.
Reason:
1. The atoms of alkaline earth metals have two delocalized electrons and their sizes are smaller than those of alkali metals.
2. Alkaline earth metals have closed-packed structure while alkali metals have open structure (body-centered cubic).
Hence, the statement (1) is correct.

All alkali metal carbonates (except lithium carbonate) are stable at a temperature around 800°C. Lithium carbonate decomposes around 700°C forming lithium oxide and carbon dioxide. The relative instability of lithium carbonate is due to the small size Li+, and hence a very large charge/radius ratio of Li+ ion.
Hence, the statement (2) is incorrect.

Alkaline earth metal ions are much smaller than alkaline metal ions and carry a higher charge. Therefore, their polarizing power is greater. Electron cloud of carbonate anions are more easily distorted by alkaline earth metal ions than by alkali metal ions. Carbonates of alkali metals are therefore less stable to heat and decompose to metal oxide and carbon dioxide. Hence, the statement (3) is incorrect.

Radium (Alkaline earth metal) and Francium ( alkali metal) are radioactive elements.