```Where, λ = wavelength , h = Planck"s constant                  Quantum Numbers
(6.626 X 10-34 Js), p = momentum, m = mass ,
v = speed                                                         A total of four quantum numbers are used
to describe completely the movement and
Heisenberg’s Uncertainty Principle                                 trajectories of each electron within an
atom.
It states that the more precisely the position of
   It can be used to determine the electron
a particle is determined, the less precisely the
configuration of an atom and the probable
momentum is known, and vice versa. In
location of the atom"s electrons.
mathematically, x. p  h / 4 
   It also used to determine other
Where, ∆x = the uncertainty in position,                           characteristics of atoms, such as ionization
∆p = the uncertainty in momentum, h =                              energy and the atomic radius.
Planck"s constant (6.626 X 10-34 Js),
So, h/4π = 0.527 x 10-34 Js
These rules are summarized as follows:
Quantum Number              Symbol            Orbital meaning                 Range of           Value
values         examples
principal                           n      shell                                1≤n             n = 1, 2, 3, ...
azimuthal or angular                l      subshell (s orbital is listed as     0≤l≤n−1         for n = 3:
0, p orbital as 1 etc.)                              l = 0, 1, 2 (s, p,
d)
magnetic or projection of          ml      energy shift (orientation of         −l ≤ ml ≤ l     for l = 2:
angular momentum                           the subshell"s shape)                                ml = −2, −1, 0,
1, 2
spin projection                    ms      spin of the electron (−1⁄2 =           −s ≤ ms ≤ s     for an
"spin down", 1⁄2 = "spin up")                          electron s = 1⁄2,
so ms = −1⁄2, 1⁄2
e.g. The quantum numbers used to refer to the outermost valence electrons of the Carbon (C) atom,
which are located in the 2p atomic orbital, are; n = 2 (2nd electron shell), l = 1 (p orbital subshell),
ml = 1, 0 or −1, ms = 1⁄2 (parallel spins).
Electron Configuration
    It is the distribution of electrons of an atom or molecule in atomic or molecular orbitals.
    It is written as nlx. Where, n = the principal quantum number, l = subshell or azimuthal quantum
number, x = the number of electrons
    Number of electrons in n shell = 2n2 e.g., in 2nd shell the number of electrons = 2 x 22 = 8.
    It is also written as 2, 8, 8, 18, 18, 32.
Element                                    Configuration
2, 8, 8 type                     nlx type
Hydrogen (1H)                  1                             1s1
Oxygen (8O)                    2, 6                          1s2, 2s2, 2p4
Magnesium (12Mg)               2, 8, 2                       1s2, 2s2, 2p6, 3s2
Calcium (20Ca)                 2, 8, 8, 2                    1s2, 2s2, 2p6, 3s2,
3p6, 4s2
262
```