Question

Principal quantum number describes
A.Shape of orbital
B.Size of orbital
C.Spin of electron
D.Orientation of in the orbital electron cloud

Answer 1

Quantum numbers are the numbers that describe the position and energy of the electrons in an atom. There are different quantum numbers. Principal quantum number is represented by n and describes the shells and size of the orbital and the energy level in which an electron is placed.

Complete answer:
There are four different quantum numbers. They are principal quantum number, azimuthal quantum number, magnetic quantum number and spin quantum number.
Principal quantum number was represented by n, which describes the energy of an electron and the distance of the electron from the nucleus.
If the principal quantum number has the value of $1$, it refers to the orbital $1s$ orbital.
If the principal quantum number has the value of $2$ , it refers to the orbital $2s,2p$orbitals.
If the principal quantum number has the value of $3$ , it refers to the orbital $3s,3p$ and $3d$ orbitals.
If the principal quantum number has the value of $4$ , it refers to the orbital $4s,4p,4d$ and $4f$ orbitals.
If the principal quantum number has the value of $5$ , it refers to the orbital $5s,5p,5d$ and $5f$ orbitals.
Thus, the principal quantum number describes the size of the orbital.
Hence option B is the correct one.

Note:
Azimuthal quantum number describes the shape of the orbital and represented by $l$, and spin quantum number describes the spin of the electron and magnetic quantum number describes the orientation of the electron cloud in the orbital. No two electrons will have the four quantum numbers as the same.