Bonding, Molecular Shape & Structure

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Slide 1

Bonding, Molecular Shape & Structure

By

Dr. Fawaz Aldabbagh

Slide 2

The Periodic Table

Slide 3

Lewis Symbols

Represent the number of valence electrons as dots

Valence number is the same as the Periodic Table Group Number

For example,

Groups 1 2 3 4 5 6 7 8

n = 1

n = 2

Slide 4

Elements want to achieve the stable electron configuration

of the nearest noble gas

Atoms tend to gain, lose or share electrons until they are surrounded by 8 electrons

Octet Rule

n = 2

n = 3

Slide 5

Nobel Gas Has a Stable Electron Configuration

Electronic configuration of Neon achieved in both cases

Example of Ionic Bonding

10

11

9

Slide 6

Ionic Bonding refers to electrostatic forces between ions, usually a metal cation and a non-metal anion

Covalent Bonding results from the sharing of two electrons between two atoms (usually non-metals) resulting in molecules

There are two types of bonding;

Octet Rule applies

Each Covalent Bond contains two electrons

Triple bond

Slide 7

Covalent Bonding – Atoms Share Electrons

Slide 8

Hydrogen molecule, H2

Concentration of negative charge between two nuclei occurs in a covalent bond

7A elements (e.g. F) have one valence electron for covalent bonding, so to achieve octet

6A elements (e.g. O) use two valence electrons for covalent bonding, so to achieve octet

5A elements (e.g. N) use three valence electrons for covalent bonding, so to achieve octet

4A elements (e.g. C) use four valence electrons for covalent bonding, so to achieve octet

Slide 9

Carbon dioxide, CO2

Double bonds

Rules for Drawing Lewis Structures

First sum the number of valence electrons from each atom

The central atom is usually written first in the formula

Complete the octets of atoms bonded to the central atom (remember that H can only have two electrons)

Place any left over electrons on the central atom, even if doing so it results in more than an octet

If there are not enough electrons to give the central atom an octet , try multiple bonds

E.g. 1. PCl3