Lewis Structure of Molecular Compounds

I. Introduction

  • Lewis structure is a representation that shows the arrangement of electrons in a molecule.

  • Focused on understanding bonding through the interaction of valence electrons.

II. Key Concepts of Lewis Structure

A. Electron Configuration and Bonding

  • Electrons are situated outside the nucleus of an atom.

  • Chemical bonds form during interactions between these electrons.

    • Types of Bonds:

      1. Ionic Bonds: Formed by the transfer of electrons from metals to nonmetals.

      2. Covalent Bonds: Formed by the sharing of electrons between nonmetals.

B. Valence Electrons

  • Valence electrons are in the outermost shell and are crucial for determining stability.

  • Octet Rule: Atoms strive for a full outer shell of 8 electrons to achieve stability.

III. Lewis Structures for Monoatomic Elements

  • Monoatomic elements require a stable octet.

A. Examples

  • Magnesium (Mg):

    • 2 dots representing its 2 valence electrons.

  • Fluorine (F):

    • 7 dots representing its 7 valence electrons.

B. Valence Electrons and Oxidation States Table

Group No.

Group No.

Valence Electrons

Number of Dots

Oxidation No.

1

1

1

+1

2

2

2

+2

3 - 12

Transition Metals

-

-

13

3

3

+3

14

4

4

±4

15

5

5

-3

16

6

6

-2

17

7

7

-1

18

8

8

0

IV. Lewis Structures for Ionic Compounds

A. Binary Ionic Compounds

  • Formed by a metal and a non-metal.

  • Metals lose electrons while non-metals gain electrons.

B. Representation

  • Ionic bonds involve transfer; represented in Lewis structure with dots.

V. Lewis Structures for Polyatomic Ions

A. Understanding Polyatomic Ions

  • Composed of covalently bonded atoms with a net charge.

B. Steps to Determine Lewis Structure

  1. Calculate total valence electrons (VET).

    • Formula: VET = Σ Valence Electrons + Number of Atoms

  2. Determine the number of bonded electrons (BE).

  3. Count required electrons (RE) for octet fulfillment.

  4. Calculate available electrons (AE) using:

    • AE = VET - RE

  5. Identify the central atom based on electronegativity.

  6. Determine bonds or lone pairs around the central atom using:

    • No. of bonds or lone pair electrons = (BE - AE) / 2