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Quantum numbers
CHEMISTRY - Secondary 2
In This part we will study:
The mathematical solution of Schrodinger's equation introduced four numbers that were called quantum numbers.
To determine the energy of an electron in multi-electron atoms, we should know the four quantum numbers which describe it, these four quantum numbers are:
 The principal quantum number (n)
(a) Bohr had used this number in explaining the spectrum of hydrogen atom, it is given the symbol (n) and it is used to define the following:
 The order of principal energy levels or electron shells. Their number in the heaviest known atom in its ground state is seven.
 The number of electrons (e-) required to fill a given energy level from the relation 2n2
(i.e. it equals two times the square of the shell number).

• The rule 2n2 isn't applied to the energy levels higher than the fourth level.
Because the atom becomes unstable, if the number of electrons exceeds 32 electrons in any level.

(b) The principal quantum number has integer number values 1 , 2 , 3 , 4 , ........ etc , excluding zero. Each value is expressed by an alphabetical letter that represents a principal energy level as shown in th.e following table :

Best wishes to you
Mr.Ahmed Elbasha

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