S-Block Elements Test - 4

Magnesium is a silvery white metal. It burns with an intense white flame, but its salts don't produce a distinct color in the flame test.

Alkaline earth elements are metallic elements found in the second group of the periodic table. All alkaline earth elements have an oxidation number of +2, making them very reactive. Because of their reactivity, the alkaline metals are not found free in nature.

MgSO₄ is soluble in water, because the hydration energy of MgSO₄ is greater than its lattice energy and the overall process is exothermic.
But in case of BaSO₄, the hydration energy is less than its lattice energy which makes the overall process endothermic.

The thermal stability of alkaline earth metal carbonates increases with increasing cationic size. Hence, the decreasing order of thermal stability of alkaline earth metal carbonates is:
BaCO₃ > SrCO₃ > CaCO₃ > MgCO₃

The thermal stability of alkaline earth metal carbonates increases as one goes down the group. This is because the charge density on the metal ion decreases and therefore, the polarising power decreases.

The increasing order of thermal stability of carbonates of alkali metals is:
BeCO₃ < MgCO₃ < CaCO₃ < SrCO₃ < BaCO₃

Be(OH)₂ can act as an acid as well as a base.
With acid: Be(OH)₂ + 2HCl → BeCl₂ + 2H₂O
With base: Be(OH)₂ + 2NaOH → Na₂[Be(OH)₄] + H₂O

Barium sulphate is used as an opaque contrast medium for X-ray examination of the digestive tract.

Mg(OH)₂ is also known as milk of magnesia. It is a mild base and is used to neutralise excess acid in the stomach.

Be⁺², owing to its smaller size and higher charge density, has a greater polarising power.
Hence, compounds of beryllium are predominantly covalent, while magnesium forms ionic compounds.