The document discusses the four quantum numbers that describe electrons in atoms: principal quantum number (n), azimuthal/angular momentum quantum number (l), magnetic quantum number (m), and spin quantum number (s). N determines the shell and average distance from the nucleus. L determines the subshell and shape. M gives orbital orientation. S indicates electron spin direction as clockwise or counterclockwise. Each number has specific allowed values and properties that provide the electron's precise location.

1. by
Dr. RANEESH KONNOLA
GWPC, THRISSUR

2.  Quantum numbers are the address of an electron.
 These are certain numbers used to explain the size, shape and
orientation of orbitals.
 There are four quantum numbers which describe the electron in
an atom. They are
1. Principal Quantum number (n),
2. Azimuthal /Angular momentum Quantum number (Ɩ),
3. Magnetic Quantum number (m or mƖ) and
4. Spin Quantum number (s)

3.  It describes the size the orbital.
 It gives the energy of electron in an orbit.
 It gives the shell in which the electron is found.
 It also gives the average distance between the electron and the nucleus.
 The possible values of n are 1, 2, 3, 4, 5 etc.
 n ≠0
 n = 1, the electron is in K shell
 n = 2, the electron is in L shell
 n = 3, the electron is in M shell

4.  It describes the shape of the orbital.
 It gives the sub shell in which the electron is located.
 It also gives the orbital angular momentum of the electron.
 For a given value of n, the possible values of l are : Ɩ = 0, 1, 2, .......... (n-1)
 For n = 1, Ɩ = 0.
 For n = 2, Ɩ = 0 and 1.
 For n = 3, Ɩ = 0,1 and 2.
 Ɩ= 0 represents s orbital,
 Ɩ = 1 represents p orbital
 Ɩ = 2 represents d orbital
 Ɩ = 3 represents f orbital

5.  It gives information about the orientation of orbitals in space.
 For a given ‘Ɩ’ value, there are 2Ɩ+1 possible values for m
 These values are given by m = – Ɩ to 0 to + Ɩ
 For Ɩ = 0, mƖ = 0.
s sub shell contains only one orbital called s orbital.
 For Ɩ = 1, mƖ = –1, 0 and +1.
p subshell contains three orbitals called p orbitals (px, py, pz)
 For Ɩ = 2, mƖ = –2, –1, 0, +1 and +2.
d sub-shell contains five orbitals called d orbitals (dxy, dxz, dyz, dx2-y2, dz2)

6.  It gives the direction of spin of electrons.
 The values for s may be +½ or -½.
 +½ represents clock-wise spin
 -½ represents anticlockwise spin

7.  The total number of sub-shells in an orbit = n
 The total number of orbitals in an orbit = n2
 The maximum number of electrons in an orbit = 2n2
 The total number of orbitals in a sub-shell = 2l + 1
 The total number of electrons in a sub-shell = 2(2l+1)= 4l +2

8. Name Symbol Allowed Values Property
Principal n 1,2,3,.. Orbital size and energy
level
Azimuthal l 0 to (n-1) Orbital shape
(subshells)
Magnetic m -l to +l Orbital orientation
Spin s + 1/2 or – 1/2 Electron spin direction