Question

An element belongs to the group$II$. What would be its valency? Write the formula of molecules of compounds it will form with elements in$VA,VIA\,$and$VIIA$groups.

Answer 1

As we know that the periodic table is the tabular display of chemical elements. These elements are arranged in the increasing order of atomic number, electronic configuration and the chemical properties. The number of unpaired electrons present in the outermost shell is known as valency. And the valency will help to predict the molecular formula of the compound.

Complete answer:
We have to know that the elements present in the group$II$ are known as alkaline earth elements and the elements are beryllium, magnesium, calcium, strontium, barium and radium. The outer electronic configuration of group two elements is $n{s^2}$. Hence, the valency of group two elements is equal to two.
And the formula of molecules of compounds it will form with elements in$VA$can be written as,
Let ‘M’ be the element present in group two and X be the element of$VA$. Then the formula is ${M_3}{X_2}$. Example, magnesium phosphide, $M{g_3}{P_2}$
The formula of molecules of compounds it will form with elements in$VIA$is$MX$. Example, magnesium oxide, MgO
And the formula of molecules of compounds it will form with elements in$VIIA$is$M{X_2}$. Example, magnesium fluoride, $Mg{F_2}$.

Note:
We need to know that the periodic table contains vertical columns and horizontal rows and it is known as groups and periods respectively. The reaction of elements mainly depends on the number of electrons present in the outermost orbital, which are known as valence electrons. And by using valency we can explain the reacting capacity of an atom with the other atom. And we can depict the property of an element by using the valency. And the valency does not contain any positive or negative sign.