Question

The long form of periodic table is nothing but just a graphical representation of principle.
A.Aufbau
B.Hund’s
C.Pauli exclusion
D.Wave mechanical

Answer 1

Hint: The periodic table is basically an arrangement of all the elements in accordance with their increasing atomic numbers and chemical properties. Moreover, it indicates the filling of electrons in different sub energy levels like s, p, d, f where the electrons enter into the maximum energy level first.

Complete step by step answer:
The modern periodic table is a new and approved version of certain models put forth by scientists in the 19th and 20th century. The main credit for this periodic table is given to the scientist known as Mendeleev. He modeled his periodic table on the basis of increasing atomic mass whereas the modern periodic law was based on the increasing order of atomic numbers.
Now, the long form of periodic table is nothing but just a graphical representation of Aufbau principle. This principle dictates the manner in which electrons are filled in the atomic orbitals of an atom in its ground state. It further states that the electrons are filled into atomic orbitals in the increasing order of orbital energy level. The available atomic orbitals with the lowest energy are occupied before those with higher energy levels. Now, a diagram illustrating the order in which the atomic orbitals are filled is as shown:
Moreover, the order in which the energy of orbitals increases can be determined with the help of $(n + 1)$ rule. If two orbitals share equal $(n + 1)$ values then the orbital with the lower ‘n’ value is said to have lower energy associated with it.

Hence, option A is correct.

Note:
It is important to note that each orbital can hold a maximum of two electrons as per the Pauli Exclusion Principle. Moreover, the manner in which electrons are filled into orbitals in a single sun shell must follow Hund’s rule i.e. every orbital in a given subshell must be singly occupied by an electron before any two electrons pair up in an orbital.