A Simple Guide to the Angular Momentum Formula in Chemistry

Angular momentum can be a tricky FSc and entry test concept to grasp. Whether you are entirely new to the concept or just need a quick refresher, look no further! We here at Out-Class have prepared a handy entry test revision guide for the angular momentum formula below.

 

Why is Angular Momentum Important in Chemistry?

In FSc Chemistry, one of the first things we learn is the atomic model. We know that electrons move in specific orbitals around an atom's nucleus. But in order to describe this circular motion of electrons, we need a quantity called angular momentum.

Whereas linear momentum p = mv is about straight-line motion, angular momentum is about spinning or rotating motion, such as that of electrons around a nucleus! 

 

 

What is the Angular Momentum Formula?

The angular momentum formula vector is given by:

L = r p

Where:

• r = radius vector

• p = linear momentum vector

As you can observe, the angular momentum vector is just the cross-product between the radius and the linear momentum. Hence, it can also be written more simply as:

L = mvr

Where: 

• m = mass

• v = velocity

• r = radius

 

What is the unit of Angular Momentum?

The SI unit and dimension of angular momentum is important to understand for FSc finals and entry tests.

The SI unit of angular momentum is:

kg m2 s-1

 

In order to arrive at these SI units, we just had to multiply the SI units of each component in the formula of angular momentum, L = mvr, as follows:

• m kg

• v m s-1

• r m

The dimension of angular momentum is:

[M][L]2[T]-1

 

Conclusion

In short, understanding the angular momentum formula in FSc and entry test Chemistry helps us figure out how electrons behave in atoms. Its formula is L = mvr and its SI units are kg m2 s-1.