Electronic Configurations of Noble Gases (or Inert Gases)
Noble gas
(Inert gas) | Symbol | Atomic number | Electronic configuration
K L M N O P | Number of electrons in
outermost shell
(Valence shell) |
|---|
1.Helium
2.Neon
3.Argon
4.Krypton
5.Xenon
6.Radon | He
Ne
Ar
Kr
Xe
Rn | 2
10
18
36
54
86 | 2
2,8
2,8,8
2,8,18,8
2.8,18,18,8
2,8,18,32,18, 8 | 2
8
8
8
8
8 |
If we look at the number of electrons in the outermost shells of the inert gases in the above table, we find that only one inert gas helium has 2 electrons in its outermost shell, all other inert gases have 8 electrons in the outermost shells of their atoms. We know that the outermost shell of an atom can accommodate a maximum of 8 electrons (except when the outermost shell is K shell and it can hold only a maximum of 2 electrons).This means that
all the noble gases have completely filled outermost shells.Since the atoms of inert gases are very stable and have 8 electrons in their outermost shells, therefore,to have 8 electrons in the outermost shell of an atom is considered to be the most stable arrangement of electrons.To have '8 electrons' in the outermost shell of an atom is known as 'octet' of electrons. Most of the inert gases have octet of electrons in their valence shells. From this discussion we conclude that
the atoms having 8 electrons (or octet of electrons) in their outermost shell are very stable and hence chemically unreactive.
Please note that 2 electrons in the outermost shell is considered to be a stable arrangement of electrons only when the atom has just one shell, K shell, and there are no other electron shells in the atom.To have '2 electrons' in the outermost K shell is known as 'duplet' of electrons. Helium is the only inert gas having a duplet of electrons in its outermost shell. It is very important to note here that
though 8 electrons in the outermost shell always impart stability to an atom, but 2 electrons in the outermost shell impart stability only when the outermost shell is the first shell (K shell),and no other shells are present in the atom.
It should be noted that noble gases are unreactive because they have very stable electron arrangements with 8 (or 2) electrons in their outermost shells. In other words,the noble gas atoms have completely filled outermost shells. It is not possible to remove electrons from the outermost shell of a noble gas atom or to add electrons to the outermost shell of a noble gas atom. Due to this the outermost electrons of a noble gas atom cannot take part in chemical reactions.
Since the atoms of inert gases are very stable or unreactive they can exist in the free state as individual atoms.So,the inert gases are monoatomic, that is,inert gases exist as single atoms. Their atoms and molecules are just the same. For example, helium, neon, argon, etc.,all exist in the form of monoatomic molecules He, Ne, Ar, etc.
Notes
Structure of the Atom - Notes
1. Drawback of Rutherford’s Model of the Atom
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2. Rutherford’s Experiment - Discovery of Nucleus
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3. For the symbols H, D and T,tabulate three sub-atomic particles found in each of them.
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4. Structure of The Atom - Study Points
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10. Arrangement Of Electrons In The Atoms
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13. Limitations of Rutherford's model of the atom
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15. How to learn naming Chemical Formulae?
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16. All about Names of the Chemical Elements
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21. Comparison between Proton, Neutron and Electron
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22. Electronic Configurations of First 20 Elements
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26. Rules for writing of distribution of electrons in various shells for the first 18 elements
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37. The Physical Properties of the Isotopes of an Element are Different
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40. All the Isotopes of an Element Have Identical Chemical Properties
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42. Relationship Between Mass Number and Atomic Number
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44. Electronic Configurations of Noble Gases (or Inert Gases)
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45. Valaence Electrons (Or Valancy Electrons)
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47. Reason for the Fractional Atomic Masses of Elements
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49. Relation Between Valency and Valence Electrons
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