Question

An element X belongs to the ${3^{rd}}$ period and group 16 of the Modern Periodic Table. Determine the number of valence electrons and the valency of X?

Answer 1

Hint: The periodic table is the table of elements where all the elements are arranged periodically according to their repeating properties. There have been many periodic tables made in the past. The modern periodic table is the latest periodic table.

Complete answer:
In the modern periodic table, the elements are sequenced as per their atomic numbers. The modern periodic table is also known as the long form of periodic table.
The modern periodic table consists of seven rows and eighteen columns. These seven rows are known as periods whereas the eighteen columns are known as groups. Each group comprises elements with similar chemical nature and in each period, the physical and chemical properties transition from left to right.
The electrons in the outermost shell of an atom and which have the ability to get transferred to another atom or can be shared with another atom, are known as valence electrons. The property of an atom to be able to bond with other atoms to obtain the most stable electronic configuration, is known as the valency of that atom. To obtain most stable electronic configuration, the outermost shell should contain eight valence electrons, also known as octet.
Throughout a group in the periodic table, all the elements have the same valency as their outer electronic configuration formula is also the same.
The element X belongs to the third period and that is why it will possess three energy shells. The element X belongs to group 16 and all the members of group 16 have the outer electronic configuration formula as $n{s^2}n{p^4}$ where n is the outermost energy shell. Hence the outer electronic configuration of element X will be $3{s^2}3{p^4}$.
Therefore, there will be 6 outermost electrons that are 6 valence electrons in element X and its valency will be 2.

Note:
Helium does not follow the octet rule as its outermost shell cannot fit more than two electrons. Hence it is already stable with two electrons achieving a duplet state. This duplet rule is applied to hydrogen and lithium too.