Tag: alkali metals

Lithium and sodium form complex hydrides such as lithium aluminium hydride and sodium borohydride.

Radium is a radioactive element. The radiations cause harms to humans on exposure.

Magnesium sulfate is highly soluble in water (Epsom salt). Calcium fluoride and barium sulfate are notoriously insoluble in water.

On moving down the group of alkaline earth metals, the solubility of metal sulphates decreases. Also, the ionic size increases and hydration energy of metal ion decreases. Hence, magnesium sulphate($MgSO _4$) has lowest solubility.

Beryllium cannot give flame test. Beryllium has small size. It strongly binds its electrons. Thus it has high ionization enthalpy. The thermal energy of flame is not sufficient to excite its electrons.

Strontium chloride($SrCl _2$) gives crimson red colour in the flame test. It is due to the excitation of electrons by the thermal energy, which is then followed by de-excitation of electron to ground state along with liberation of light in the visible range.

Action of oxidizing agents such as conc. nitric acid forms a layer of an oxide on the surface of Be and Al. Hence these metals become passive and do not react.

Strontium sulphate crystalizes without water of hydration.

Small sized Be and Mg atoms have high ionization energies. Hence, the energy of flame is not sufficient to excite their electrons. Thus, Be and Mg do not produce colour in flame.