Principle quantum number {eq}\left( n \right){/eq} Since it is the first of four different quantum numbers; we can call it the first quantum number as well. They can even take on more complex shapes as the value of the angular quantum number becomes larger. Quantum Number. A principal quantum number is a quantum number that describes the main energy level in which an electron exists. An atom consists of a large number of orbitals which are distinguished from each other on the basis of their shape, size and orientation in space. What is Principal Quantum Number? Based on above, the electron are filled in below order of the orbitals. 2. The Pauli exclusion principle has the net effect of limiting the number of electrons that can be assigned a shell-subshell combination of quantum numbers. We can denote it as “n”. The principal quantum number therefore indirectly describes the energy of an orbital. The Principal Quantum Number, represented by the letter n, is used to define the energy level of the electron in any atom. The orbital characteristics are used to define the state of an electron completely and are expressed in terms of three numbers as stated, Principal quantum number, Azimuthal quantum number and Magnetic quantum number and Spin Quantum … The principal quantum number is: {eq}n = 3{/eq}. As previously stated, the core electron shell is that with the lowest energy and, therefore, would have a lower principal number. The sum of the values of the principal quantum numbers (n) and azimuthal quantum number (l) i.e (n+l) determined the energy level of an orbital. Orbitals have shapes that are best described as spherical (l = 0), polar (l = 1), or cloverleaf (l = 2). 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 4f,5d, 6p, 7s. For example, in any s subshell, no matter what the shell number, there can be a maximum of only two electrons. Four quantum numbers can describe an electron in an atom completely: Principal quantum number (n) Azimuthal quantum number (ℓ) Magnetic quantum number (m ℓ) Spin quantum number (s) The spin-orbital interaction, however, relates these numbers. The Principal Quantum Number ($$n$$) The principal quantum number, $$n$$, designates the principal electron shell. In chemistry, the electron’s energy level is also referred to as the energy shell. It is denoted by n.Thus, n = 1, 2, 3, 4…It is one of the four quantum numbers that identify an electron in the atom; the others are the azimuthal quantum number, the magnetic quantum number, and the spin quantum number. Pauli exclusion Principle which states no two electrons can have same set of 4 quantum no. The principal quantum number is a set of positive integers that decide the size and energy of an orbital. The angular quantum number (l) describes the shape of the orbital. In quantum physics, there are four quantum numbers that expresses an electron in an atom.