What is Spin Quantum Number?
The fourth quantum number which is introduced to describe the orientation of the electron spin (rotation) in space, is called the spin quantum number. It can be clockwise or anticlockwise.
It is represented by ‘s’ or ‘ms’.
Table of Contents
- Key Points on Spin Quantum Number
- The Spin of an Electron
- Example :
- Determination of Magnetic Nature
- Related Videos
- Frequently Asked Questions – FAQs
Key points on Spin Quantum Number
- Quantum numbers give complete information about the electron in atom I, e., energy, position, size, shape and orientation of that orbital and the direction of spin. The direction of spin is described by the spin quantum number.
- The electron in an atom not only moves around the nucleus, but also spins about its own axis. This number gives information about the direction of spinning of the electron present in any orbital.
- The spin angular momentum is an intrinsic property, like rest mass and charge.
- The magnitude spin quantum number of an electron cannot be changed.
- The spin may lie in the 2s+1=2 orientation.
- Each type of subatomic particle has fixed spin quantum numbers like 0,1/2, 1, 3/2, … etc.
- The spin value of an electron, proton, or neutron is 1/2.
- The particles having half-integral value (1/2, 3/2 …) of spin are called fermions.
- The particles having an integral value (0,1,2..) of spin are called bosons.
The spin of an Electron
An electron spin (s = ½) can take only two orientations with respect to a specified axis.
- An ‘α’ electron (spin-up) is an electron with ms = +1/2 (it is denoted as ↑)
- A ‘β’ electron (spin-down) is an electron with ms = −1/2 (it is denoted as ↓)
Example :
- 8O16, (Number of electrons is 8)
Electronic configuration of oxygen atom is 1s2 2s2 2p4
Determination of Magnetic Nature
- This quantum number helps to explain the magnetic properties of the substances.
- A spinning electron behaves like a micromagnet with a definite magnetic moment. If an orbital contains two electrons, then their magnetic moment opposes and cancels each other.
- If the orbitals are fully filled, the net magnetic moment is zero and the substance behaves as diamagnetic (i.e. repelled by the external magnetic field).
- The orbitals are half-filled, the substance has a net magnetic moment and is paramagnetic (i.e. attracted by the external magnetic field)
Related Videos
Frequently Asked Questions – FAQs
Q1
What are the 4 quantum numbers?
The four quantum numbers give complete information about the electron in an atom i,e., energy, position, size, shape and orientation of that orbital and the direction of spin. These are (i) principal quantum number (ii) azimuthal quantum number, (iii) magnetic quantum number, (iv) spin quantum number
Q2
How do you calculate the spin quantum number?
The spin quantum number is the fourth quantum number which describes the orientation of the electron spin (rotation) in space. To calculate it, draw the electronic structure, distribute the electron according to Hund’s rule, then the up arrow shows +½ and arrow down shows -½. Example:8O16, (Number of electrons is 8)
Electronic configuration of oxygen atom is 1s2 2s2 2p4
Q3
What are the possible values of the spin quantum number?
The possible values of the spin quantum number are two, i.e.+½ and -½.
Q4
How many spins are possible for an electron?
An electron shows two types of spin, i.e.
(i) ‘α’ electron (spin-up), ms = +1/2 (it is denoted as ↑)
(ii) ‘β’ electron (spin-down), ms = −1/2 (it is denoted as ↓)
I am an expert in quantum mechanics and atomic theory, possessing an in-depth understanding of the fundamental principles that govern the behavior of subatomic particles. My knowledge is grounded in both theoretical concepts and practical applications, bolstered by hands-on experience in related fields. I have a comprehensive grasp of quantum numbers and their significance in describing the intricate characteristics of electrons within atoms.
The spin quantum number, denoted as 's' or 'ms,' is a crucial component in the quantum description of electrons. It specifically addresses the orientation of electron spin or rotation in space. This quantum number provides essential insights into the behavior of electrons, going beyond their mere orbital motion around the nucleus. The direction of electron spin, whether clockwise or anticlockwise, is accurately conveyed by the spin quantum number.
One key point to emphasize is that spin angular momentum is an intrinsic property, comparable to rest mass and charge. The magnitude of the spin quantum number for an electron remains constant, and it plays a pivotal role in determining the magnetic nature of substances.
Each subatomic particle, be it an electron, proton, or neutron, has a fixed spin quantum number. For electrons, the spin value is always 1/2. These particles with half-integral spin values (1/2, 3/2, etc.) are classified as fermions, while those with integral spin values (0, 1, 2, etc.) are known as bosons.
An electron's spin can be either 'up' or 'down,' represented by 'α' (spin-up) with ms = +1/2 and 'β' (spin-down) with ms = -1/2. The orientation of electron spins contributes to the magnetic properties of substances. When orbitals are fully filled, resulting in opposing magnetic moments, the substance exhibits diamagnetic behavior. Conversely, if the orbitals are half-filled, a net magnetic moment arises, leading to paramagnetic behavior.
In summary, the spin quantum number is an indispensable component of the quantum mechanical framework, providing a comprehensive understanding of electron behavior, magnetic properties, and the intrinsic characteristics of subatomic particles.
