Lewis symbol is a symbol in which the electrons in the valence shell of an atom or simple ion are represented by dots placed around the letter symbol of the element. Each dot represents one electron.
| Hydrogen |  |
| Oxygen |  |
| Chlorine |  |
| Chloride ion |  |
|
A
covalent bond is a chemical bond formed by the sharing of a pair of electrons between two atoms.
The
Lewis structure of a covalent compound or polyatomic ion shows how the valence electrons are arranged among the atoms in the molecule to show the connectivity of the atoms.
Instead of using two dots to indicate the two electrons that comprise the covalent bond, a line is substituted for the two dots that represent the two electrons.
Below is shown the Lewis structure for water. Two hydrogens (H) are separately covalently bonded to the central oxygen (O) atom. The
bonding electrons are indicated by the dashes between the oxygen (O) and each hydrogen (H) and the other two pairs of electrons that constitute oxygens octet, are called
non-bonding electrons as they are not involved in a covalent bond.
- The first step in drawing Lewis structures is to determine the number of electrons to be used to connect the atoms. This is done by simply adding up the number of valence electrons of the atoms in the molecule.
Consider carbon dioxide CO
2 carbon (C) has four valence electrons x 1 carbon = 4 e-
oxygen (O) has six valence electrons x 2 oxygens = 12 e-
There are a total of 16 e- to be placed in the Lewis structure.
- Connect the central atom to the other atoms in the molecule with single bonds.
Carbon is the central atom, the two oxygens are bound to it and electrons are added to fulfill the octets of the outer atoms.
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