Question

Is potassium an alkaline earth metal?

Answer 1

The elements which are present in group I of the periodic table are known as alkali metals while the elements which are present in the group II of the periodic
table are known as alkaline earth metals.

Complete answer:
The group I of the periodic table contains metals which are known as the alkali metals. They have a single electron in their outermost shell and by removing this electron they can attain a noble gas configuration which is highly stable. Hence they are very reactive in nature.
The alkali metals are Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs) and Francium (Fr).
The alkali metals react vigorously with water forming soluble hydroxides which are called alkalis. This is the reason why these metals are called alkali metals. Let us see the example of alkali formation.
$\underset{\text{Alkali Metal}}{\mathop{2K}}\,+2{{H}_{2}}O\to \underset{\text{Alkali}}{\mathop{2KOH}}\,+{{H}_{2}}$
The group II of the periodic table contains metals which are known as alkaline earth metals. They have two electrons in their outermost shell and by removing these electrons they can attain a noble gas configuration which is highly stable. Hence they are also very reactive in nature.
The alkali metals are Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba) and Radium (Ra).
The alkaline earth metals form oxide in the earth and they are soluble in water. This is the reason they are named so.
$\underset{\text{Alkaline Earth Metal}}{\mathop{CaO}}\,+{{H}_{2}}O\to \underset{\text{Slaked Lime}}{\mathop{Ca{{\left( OH \right)}_{2}}}}\,$
Hence potassium is an alkali metal and not an alkaline earth metal.

Note:
Alkali metals are more reactive than alkaline earth metal due to the presence of a single electron in the valence shell. They should be handled with care and proper protection should be taken while using them in the lab.