Angular momentum of an electron is quantized.

Explanation:
The concept of quantization was introduced by the Danish physicist Niels Bohr in 1913 to explain the stability and energy levels of electrons in an atom. According to Bohr's model, electrons can only occupy certain discrete energy levels or orbits around the nucleus, and the angular momentum of the electron is quantized.

Angular momentum:
Angular momentum is a property of a rotating or revolving object. For an electron in an atom, the angular momentum is given by the product of its mass, velocity, and radius of the orbit. Mathematically, it is represented as:

L = mvr

Where L is the angular momentum, m is the mass of the electron, v is its velocity, and r is the radius of the orbit.

Quantization of angular momentum:
According to the principles of quantum mechanics, the angular momentum of an electron in an atom is quantized, meaning it can only have certain discrete values. The quantization of angular momentum is a consequence of the wave-particle duality of electrons.

Quantum numbers:
The quantization of angular momentum is described by the quantum numbers. The principal quantum number (n) determines the energy level or the size of the orbit, while the azimuthal quantum number (l) determines the shape of the orbit. The azimuthal quantum number l also determines the allowed values of the angular momentum.

The angular momentum of an electron in an atom is quantized according to the following relation:

L = √(l(l+1)ħ)

Where ħ (pronounced "h-bar") is the reduced Planck's constant (h/2π) and l is the azimuthal quantum number.

Conclusion:
In conclusion, the angular momentum of an electron in an atom is quantized, meaning it can only have certain discrete values. This quantization is a fundamental principle of quantum mechanics and is described by the quantum numbers. The quantization of angular momentum explains the stability and energy levels of electrons in an atom.