S-Block Elements Test - 1

Among the given options, Francium, Radium and Uranium are radioactive, however, Francium is the only radioactive alkali metal.

Lithium halides are somewhat covalent because of the high polarisation capability of lithium ion. The Li⁺ ion is very small in size and has high tendency to distort electron cloud around the negative halide ion.

The ionisation enthalpies of alkali metals are considerably low and decrease down the group from Li to Cs.

Alkali metals and their salts impart characteristic colour to an oxidising flame.

Metal Colour

Li Crimson red 

Na Yellow

K Violet

Rb Red violet

Cs Blue

On moving down the group, basic character of alkali metal hydroxides increases with increasing atomic number.

Na is the most abundant alkali metal in the earth's crust. The abundance of a chemical element measures how relatively common (or rare) the element is or how much of the element is present in a given environment by comparison to all other elements.

Among metals, the alkali metals have low melting points, which decrease further on moving down the group.
Caesium or cesium is a chemical element with symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28°C (82°F), which makes it one of the only five elemental metals that are liquid at (or near) room temperature.

During the electrolysis of aqueous solution of s-block elements, H₂ gas is obtained at cathode. Alkaline earth metals are strong reducing agents . So, their oxides and halides cannot be reduced by any other elements.

Barium gives grassy green colour in flame.

Plaster of Paris is made by heating the mineral gypsum. When gypsum is heated to about 150°C, it loses water and produces the powder 'plaster of Paris'.

2CaSO₄·2H₂O + heat → 2CaSO₄·½H₂O + 3H₂O