Periodic table alkali metals

Introduction :   

Elements belonging to group 1in periodic table are called alkali metals.  Their outer most electronic configuration is ns1 in periodic table.

Z        Element        No. of electrons

1         Hydrogen             1

3         Lithium                2, 1

11       Sodium               2, 8, 1

19       Potassium           2, 8, 8, 1

37       Rubidium            2, 8, 18, 8, 1

55      Caesium              2, 8, 18, 18, 8, 1

87      Francium             2, 8, 18, 32, 18, 8, 1

The group in a periodic table also includes hydrogen because of the similarity in the electronic configuration with these elements.  They are called alkali metals since they readily dissolve in water to form soluble hydroxides which are strongly alkaline in nature.  The word alkali has been derived from the Arabic word alquili, which means the ashes of plants from which certain compound of the elements sodium and potassium were initially isolated.  Sodium and potassium are abundant while the remaining elements occur only in traces.  The last element francium is radioactive and unstable. 

Alkali metals of periodic table:

They have maximum value of atomic radii, form monovalent  cations and possess the lowest ionization enthalpies  Their hydration enthalpies are low due to their large size. They have low electro negativities and all the members are strongly electro positive.They possess +1 oxidation state, and have low melting and boiling points. They are very light and impart characteristic colors to the flame.They exhibit photoelectric effect. 

They are highly reactive chemically because of their low ionization enthalpies and enthalpy of atomization. They are normally kept in chemically inert solvents such as kerosene.  They form oxide when they combine with oxygen and hydroxide when they react with water.The reaction with water is highly exothermic.So, alkali metals are not kept in contact with water.All alkali metals combine with hydrogen upon heating to form colorless crystalline hydrides that are ionic in nature.They combine with halogens directly to form metal halides. The alkali metals are powerful reducing agents.They are soluble in liquefied ammonia.They react with sulphur and prosperous upon heating to form the corresponding sulphides and phosphides.