Lewis Structure

Tags

Chem/Molecule

Cegep/2

Word count

187 words

Reading time

2 minutes

2D diagram of electron bonds in a molecule

Steps:

1. Determine the skeleton structure of the compound
   • In general, ==the least electronegative atom occupies the central position.==
   • Prefer symmetry if possible
2. Compute the total number of valence electrons
3. Draw bonds using lone pairs to respect the octet rule

[!abstract]+ Octet rule
Rule of thumb that states:

• A main-group element tends to form bonds until it has eight valence electrons.
• Carbon usually forms four bonds (no lone pairs).
• Halogens in terminal position only form single bonds.
  • Fluorine must be in terminal position.

Exceptions:

• Expanded octet: more than eight valence electrons
  • Central atoms from 3^rd period and beyond might have an expanded octet.
• Incomplete octet: less than eight valence electrons

[!abstract] Duet rule
Rule of thumb that states the valence shells of hydrogen and helium are complete with only two valence electrons

Examples

$\mathrm{NF}{\phantom{A}}_3$

Lewis 1

$\mathrm{HNO}{\phantom{A}}_3$

Lewis 2

$\mathrm{CO}{\phantom{A}}_3{\phantom{A}}^{2-}$

Lewis 3

$\mathrm{H}{\phantom{A}}_3\mathrm{O}{\phantom{A}}^{+}$

Lewis 4

$\mathrm{ClF}{\phantom{A}}_3$

Lewis 5

$\mathrm{C}{\phantom{A}}_2\mathrm{H}{\phantom{A}}_4$

Lewis 6

$\mathrm{H}{\phantom{A}}_2\mathrm{CO}$

Lewis 7

Contributors

Ajitani Hifumi

Changelog

Last edited about 2 hours ago

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