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# Inorganic Pharmaceutical Chemistry 2

الكلية كلية العلوم للبنات     القسم قسم الكيمياء     المرحلة 2
أستاذ المادة محمد حامد سعيد الدهيمي       21/12/2012 18:38:28
Inorganic Pharmaceutical Chemistry
Lecture No. 2 Date :11/10 2012
Dr. Mohammed Hamed
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Quantum Numbers
The relation of a particular electron to the nucleus can be described through a series of four numbers, called the Quantum Numbers. The first three of these numbers describe the energy (Principle quantum number), shape (Angular momentum quantum number), and orientation of the orbital (magnetic quantum number). The fourth number represents the "spin" of the electron (spin quantum number). The four quantum numbers are described below.

1. Principal Quantum Number (n): n = 1, 2, 3, …, ?
Specifies the energy of an electron and the size of the orbital (the distance from the nucleus of the peak in a radial probability distribution plot). All orbitals that have the same value of n are said to be in the same shell (level). For a hydrogen atom with n=1, the electron is in its ground state; if the electron is in the n=2 orbital, it is in an excited state.
Electrons are negatively charged, so electrons that are closer to the positively charged nucleus are more powerfully attracted and tightly bound than those that are farther away. Electrons that are closer to the nucleus are thus more stable, and less likely to be lost by the atom. In other words, as n increases, so does the energy of the electron and the likelihood of that electron being lost by the atom.
2 .The next quantum number, represented by l and called the "angular quantum number," can be any value in the range 0 , 1, 2 , ... n - 1. Specifies the shape of an orbital with a particular principal quantum number. The secondary quantum number divides the shells into smaller groups of orbitals called sub shells (sublevels). Usually, a letter code is used to identify l to avoid confusion with n:
l 0 1 2 3 4 5 ...
Letter s p d f g h ...
For example: when n = 1, l can only equal 0; meaning that shell n = 1 has only an s orbital (l = 0). when n = 3, l can equal 0, 1, or 2; meaning that shell n = 3 has s, p, and d orbitals.