What do you understand by the term Quantum Number? Explain the
four quantum numbers and their significance in characterising an
electron in the atom
Answers
The set of numbers used to describe the position and energy of the electron in an atom are called quantum numbers. There are four quantum numbers, namely, principal, azimuthal, magnetic and spin quantum numbers. The values of the conserved quantities of a quantum system are given by quantum numbers.
To completely describe an electron in an atom, four quantum numbers are needed: energy (n), angular momentum (ℓ), magnetic moment (mℓ), and spin (ms). The first quantum number describes the electron shell, or energy level, of an atom.
Quantum numbers are the numbers which give us an estimate of the probable location of an electron in an atom.
There are 4 quantum numbers,
1. Principal Quantum No(n). - This number describes the electron levels of an atom. It signifies the size of electron cloud. It can have values such as 1,2,3,4 & so on.
2. Azimuthal Quantum No(l)- This number signifies the shape of electron cloud. It can have values from l=0 to l=n-1
3. Magnetic Quantum No(m) - this signifies the orientation of electron cloud. It can have values from -l to +l including zero.
4. Spin Quantum No(s) - This signifies the spin of electrons can have. It can have values ±1/2 for each value of m.