The general properties of the alkali metals in the modern periodic table
The alkali metals are located on the left side of the modern periodic table in group ( 1 ) or ( 1 A ) . They are the first group of s – block , The alkali metals are mono-valent elements as they have only one electron in their outermost energy levels .
The alkali metals are all metals which have one electron in the outer shell , They are very reactive , they are the most reactive metals where they are located in group 1 , The alkali metals are good conductors of the heat and the electricity .
Most of the alkali metals have low density . Lithium ( Li ) . Sodium ( Na ) and potassium ( K ) elements float on the water surface as their densities are smaller than the water density . Rubidium (Rb ) and cesium ( Cs ) elements sink in the water as their densities are greater than the water density .
The alkali metals tend to lose their valency ( outermost ) electrons during the chemical reactions forming positive ions , Each of them carries one positive charge .
The elements of the alkali metals react with the water forming the alkaline solutions , So , They named the alkali metals .
The alkali metals react to lose the electrons , These metals are very reactive with reactivity increasing down the group , They are active elements , so , they are kept under the surface of kerosene or paraffin oil .
Lithium is not kept under the surface of kerosene as it floats on its surface and burns at once so , it is kept in paraffin oil , Sodium and potassium are kept under the surface of kerosene to prevent them from the reaction with the moist air as they are active metals .
If you would like to know why Cesium is the most active metal , Look at the modern periodic table , You will know that the chemical activity of the alkali metals increases as the atomic size increases therefore , Cesium ( Cs ) is considered the most active metal ( in the periodic table ) as it has the largest atomic size .