S-Block Elements Test - 14

BeCl₂ exists as a polymer in solid state. In this case Be atom is tetrahedrally surrounded by four chlorine atoms.

The alkaline earth metals are all of theelements in the second column (column 2A) of the periodic table. This group includes beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). Alkaline earth metalshave only two electrons in their outermost electron layer.

In the periodic table, the element with atomic number 38 belongs to period V and group II. It is a s-block element. It is called an alkali earth metal.

Radium belongs to group 2, which is an alkaline earth metal group. So, oxide of radium will be basic in nature.

Due to the formation of oxide layers on their surface, Be and Mg do not react with water.

Along the period, effective nuclear charge dominates. So electrons will be pulled by more force in alkaline earth metal than in alkali metal. So the ionisation potential of alkaline earth is more than alkali metals.

The elements in Group 2 (beryllium, magnesium, calcium, strontium, barium, and radium) are called the alkaline earth metals . These elements have two valence electrons, both of which reside in the outermost s sublevel. The general electron configuration of all alkaline earth metals is ns².

Beryllium and magnesium atoms are smaller in size and their electrons are strongly bound to the nucleus. They need large amounts of energy for excitation of electrons to higher energy levels which is not available in the bunsen flame. So they do not impart colour to the flame.

2Mg(NO₃)₂ → 2MgO + 4NO₂ + O₂

Since the magnesium or its compound does not give flame test, it must be a compound of calcium. Also the gas evolved is brown coloured shows that it is the oxide of nitrogen. All these inference indicates towards the compound calcium nitrate.