An element 'X' atomic number 51 belongs to ______
A.S-block
B.P-block
C.D-block
D.F-block

Hint: To answer this question, you should recall the formation of the periodic table and the filling of orbitals according to their energies. Modern Mendeleev's law states that the physical and chemical properties of elements are the periodic function of their number.


Complete Step by step solution:
There are 4 blocks within the periodic table: s-block, p-block, d-block and f-block. All of the s-block elements are metals. Usually, they're shiny, silvery, good conductors of warmth and electricity, and lose their valence electrons easily.
The p-block has the most important sort of elements and is the only block that contains three sorts of elements: metals, nonmetals and metalloids.
The d-block elements have properties that are between s-block elements and p-block elements properties. It consists of transition metals. The f-block elements are mostly radioactive. The block names were created to represent the standard of the spectroscopic lines of the atomic orbitals.
Trick to find group no.
\[{\text{The atomic no}}{\text{. of higher noble gas }} - {\text{ The given atomic no }} = {\text{ n}}\]
Group no\[ = 18 - n\]
(Exception is f-block elements)
For the element with atomic no. 51:
The atomic no. of higher noble gas is 54, i.e. of Xenon.
Thus, \[n = 54 - 51 = 3\]
Group no\[ = 18 - {\text{ }}3 = 15\]
Hence, the given element is p-block.
Therefore, we will conclude that the right answer to the present question is option A.

Note:You should know that the period of a component corresponds to the principal quantum number of the Valence shell. The block of a component corresponds to the sort of orbital which receives the last electron.
The group of a component is predicted from the amount of electrons within the Valence shell or/and penultimate shell as follows:-
• For s-block elements , group number is equal to the amount of valence electrons.
• For p-block elements ,group number is equal to \[10 + {\text{number of electrons\;within the\;Valence shell}}\].
• For d-block elements group number is equal to the amount of electrons in:
   \[\left( {n - 1} \right){\text{ d subshell }} + \;{\text{the amount\;of electrons in Valence shell}}\].