Question

Name three elements that have two electrons in their outermost shell.

Answer 1

The electrons that are present in the outermost shell are known as the valence electrons. The no. of electrons an atom donates or accepts to form a bond is known as the valency of the atom.

Complete answer:
We know that every atom of an element accepts or loses its electron to gain the Noble gas configuration. The Noble gases are the most stable elements in the universe and every atom tries to attain the Noble gas configuration, by bond formation.
The simplified version of the electronic configuration of an atom can be written by using the Noble gases. If an electron has seven electrons in the outermost shell, it’ll accept one electron to attain the stable electronic configuration. Elements like Carbon which have four valence electrons, don't fully gain or lose their electrons. Instead, they form covalent bonds by sharing electrons.
The Noble gases configurations are: $2(He),10(Ne),18(Ar),36(Kr),54(Xe)$ and every atom tries to attain these configurations.
The elements in the second group of the periodic table, have two electrons in their outermost shell. The elements that belong to the Group II are, Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba) and Radium (Ra). These groups of elements are known as the Alkaline Earth Metals. They have the third largest size of the atom; first being the Noble Gases and Alkali metals respectively.

Note:
The compounds of Alkaline Earth Metals like Limestone are used in paints as a white pigment. Calcium Chloride is used as a Deicer. Strontium is used in fireworks and Barium is used in Rubber industry, paints, plastics, resins etc.