2. Chameli Devi Group of
Institutions
PPT Presentation :Engineering Chemistry (BT-101)
Presented To : Ms. Surbhi Jain
Presented By: Ambika Mishra
( CS221021 )
3. Quantum Number
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
4. Four quantum numbers can be used to completely describe all
the attributes of a given electron belonging to an atom, these
are:
1. Principal quantum number, denoted by n.
2. Orbital angular momentum quantum number (or azimuthal
quantum number), denoted by l.
3. Magnetic quantum number, denoted by ml.
4. The electron spin quantum number, denoted by ms.
5. Principal Quantum Number
● Principal quantum numbers are denoted by the symbol ‘n’. They
designate the principal electron shell of the atom
● The value of the principal quantum number can be any integer with a
positive value that is equal to or greater than one.
Azimuthal Quantum Number
The azimuthal (or orbital angular momentum) quantum number describes
the shape of a given orbital. It is denoted by the symbol ‘l’
A value of azimuthal Quantum number indicate either s,p,d,f subshell
which vary in shape.The value depends on the value of principal quantum
number ,(i.e.) the value of azimuthal Quantum number ranges between 0
and (n-1)
6. Magnetic Quantum Number
The total number of orbitals in a subshell and the orientation of these
orbitals are determined by the magnetic quantum number. It is denoted
by the symbol ‘ml’.
Electron Spin Quantum Number
The electron spin quantum number is independent of the
values of n, l, and ml. The value of this number gives insight into
the direction in which the electron is spinning, and is denoted by
the symbol ms.
7. Eelectron Distribution
The maximum number of electrons that can be accommodated in a
shell is based on the principal quantum number (n).
It is represented by the formula 2n2, where ‘n’ is the shell number.
Shell and ‘n’ value Maximum electrons present in the
shell
K shell, n=1 2*1
2
= 2
L shell, n=2 2*2
2
= 8
M shell, n=3 2*3
2
= 18
N shell, n=4 2*4
2
= 32
8. All the possible subshells for values of n up to 4 are tabulated below.
Principle Quantum Number Value Value of Azimuthal Quantum Number Resulting Subshell in the Electron
Configuration
n=1 l=0 1s
n=2 l=0 2s
l=1 2p
n=3 l=0 3s
l=1 3p
l=2 3d
n=4 l=0 4s
l=1 4p
l=2 4d
l=3 4f
9. Filling of Atomic Orbitals
Aufbau Principle
The Aufbau principle dictates that electrons
will occupy the orbitals having lower energies
before occupying higher energy orbitals.
The energy of an orbital is calculated by the sum
of the principal and the azimuthal quantum numbers.
According to this principle, electrons are filled in the
following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p
, 6s, 4f, 5d, 6p, 7s, 5f, 6d,
10. Orbitals - Orbital Energy
The energy of an electron in a
single atom can be determined
solely by the principal quantum
number. Orbitals can be ranked
in the increasing order of orbital
energy as follows: 1s < 2s = 2p < 3s
= 3p = 3d <4s = 4p = 4d= 4f.
The energy of an electron in multi-
electron atoms depends on both its
principal quantum number (n) and
its azimuthal quantum number (l).
