Chapter 2, Problem 1CQ

To determine

The principle that summarises that no two electrons having the same space can have same quantum numbers.

Answer to Problem 1CQ

The Pauli Exclusion Principle states that no two electrons occupy the same space can have the same quantum numbers.

Explanation of Solution

The set of values which describes the electron state including the orientation of an electron, its distance from the nucleus and type of orbital, where the electron is found and its spin is known as quantum number.

There are four types of quantum number:

1. Principal Quantum number
2. Azimuthal Quantum number
3. Magnetic Quantum number
4. Spin Quantum number

The quantum number that is assigned to all electrons in an atom for the description of state of those electrons is known as Principal quantum number.

The quantum number which describes the shape of the orbital in which electron is present is known as Azimuthal quantum number.

The quantum number which describes the levels of energy in a subshell is known as Magnetic quantum number.

The quantum number which describes spin of electrons (up or down) is known as Spin quantum number.

Bonding energy depends upon the quantum mechanics and the models of the electrons based on their quantum numbers. Various principles illustrate the various laws of the electron models.

Pauli Exclusion Principle: Two electron of same atom cannot have same quantum numbers.

Let us take the example of $\text{He}\left(2\right)\to 1{\text{s}}^2$. The principle quantum number of He is 1. Azimuthal quantum number is 0, its magnetic quantum number is 0 and its spin number is $\pm \frac{1}{2}$.

Conclusion:

The Pauli Exclusion Principle summarises that two electrons occupying the same space cannot possibly have the same quantum number as a whole.