Question

An Alkaline earth metal in period $3$ is?

Answer 1

Periodic table is defined as an arrangement of elements in the increasing order of the atomic number. They are arranged left to right and top to bottom. It consists of horizontal rows known as periods and vertical columns known as groups.

Complete answer:
Alkaline earth metal is defined as the elements that are present in group $2$ of the periodic table. The group two elements have valency $2$. They can easily donate two electrons to attain the nearest noble gas configuration.
We know, elements are placed in a period according to their number of subshells present in their atoms. An element of period $3$ will possess $3$ subshells.
We can easily figure out the electronic configuration of the element- $2,8,2$
The Atomic Number of an Element is equal to the number of electrons present in an atom of the element. The total number of electrons in the above configuration is $12$. Therefore, the atomic number of the element is $12$ and the element is Magnesium $Mg$.
Alkaline earth metal in period $3$ is Magnesium $Mg$.

Note:
The electronic configuration of an atom is defined as a representation of arrangement of electrons that are distributed in the orbital of an atom. The electronic configuration helps in determining the position of an element and the chemical behavior. Alkaline earth metals possess metallic character due to their ability to donate electrons. They are called alkaline earth metals because their oxides on reaction with water form a basic solution.