CLASS :- 11
Topic :- Lewis symbols
Lewis symbols: G.N. Lewis introduced simple notation of valency electron
Symbols of the elements
with their number of valence electrons represented as dots
its do not visualize the
electrons in the inner principal energy levels.
Lewis symbols (also known as Lewis dot diagrams or electron
dot diagrams) are diagrams that represent the valence electrons of an atom (Electrons that are not in the valence level
are not shown in the Lewis symbol).
Lewis structures (also
known as Lewis dot structures or electron dot structures) are diagrams that
represent the valence electrons of atoms within a molecule.
These Lewis symbols and Lewis structures help visualize the
valence electrons of atoms and molecules, whether they exist as lone pairs or
within bonds.
Lewis
Symbols
In the Lewis symbol for
an atom, the chemical symbol of the is written, and the valence electrons or
outer shell electron are represented as dots surrounding it. Only the electrons
in the valence level are shown using this notation not inner shell electrons
. example , the Lewis
symbol of carbon depicts a “N’ surrounded by 5 valence electrons because carbon
has an electron configuration of 1s22s22p3.
Electron dots symbol of second period atoms
Why inner electrons not show in Lewis symbol ?
Electrons that are not in the valence level are not shown in
the Lewis symbol. The reason for this is that the chemical reactivity of an
atom of the element is solely determined by the number of its valence electrons, and not its inner electrons. Lewis symbols for atoms are combined to
write Lewis structures for compounds or molecules with bonds between atoms
Procedure
for Drawing Simple Lewis Structures
We have looked at how to
determine Lewis structures for simple molecules. The procedure is as follows:
1. Write a structural
diagram of the molecule to clearly show which atom is connected to which
(although many possibilities exist, we usually pick the element with the most
number of possible bonds to be the central atom).
2. Draw Lewis symbols of the
individual atoms in the molecule.
3. Bring the atoms together
in a way that places eight electrons around each atom (or two electrons for H,
hydrogen) wherever possible.
4. Each pair of shared
electrons is a covalent bond which can be represented by a dash
Lewis symbol represent number of valence electron
with the help of Lewis symbol , we predict group valency of the element
The group valency of an element is either equal to number of dots in the Lewis symbol or it is equal to 8 minus the number of dots