The s-Block Elements Test - 3

As the size increases positive charge density decreases so hydration energy also decreases. Hydration veries inversely with size

Monovalent sodium and potassium ions and divalent magnesium and calcium ions are found in large proportions in biological fluids. These ions perform important biological functions such as maintenance of ion balance and nerve impulse conduction

Ra is found in Uranium and thorium ores in trace amounts as small as a seventh of a gram per ton of uraninite  so it is rarest of all alkaline earth  metals

Na and K are highly abundant. Constituting 2.5 and 2.4 percent of the Earth's crust respectively the othwe alkali metals are  considerably rare.

The general electronic configuration of alkali metals is  ns¹ as their outer most electron enters the S orbital and they have only on electon in their velence shell. 

The general electronic configuration of ns² exists in alkaline earth metals as their outer most electron enter the S orbital  and they have only two electrons in their valence shell

Alkali metals have one unpaired electron in their valence shell which gets excited by absorbing the energy from flame, excited states  are very unstable and quickly move back to lower state ,at that time they emit the energy in the form of radiation  in visible reason of electromagnetic spectrum  and is abserved as characteristic colour. 

Flame photometry is used to determine the concentration of alkali metalions, alkaline earth metals are quite sensitive to flame photometry.

Francium will fill orbitals all the way up to 7S (7^th period) subshell whrer it will have half filled orbital : 7S¹ .

alkali metals burns vigorously to form superoxides. Superoxide O₂^- ion is only in the presence of large cations such as potassium, Rb and Cs