Chemical bonding

High School Chemistry Rapid Learning Series - 15

© Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 1

Rapid Learning CenterChemistry :: Biology :: Physics :: Math

Rapid Learning Center Presents …p g

Teach Yourself High School Chemistry in 24 Hours

1/32 http://www.RapidLearningCenter.com

Chemical Bonding

HS Ch i t R id L i S i

Rapid Learning Centerwww.RapidLearningCenter.com/© Rapid Learning Inc. All rights reserved.

HS Chemistry Rapid Learning Series

Wayne Huang, PhDKelly Deters, PhDRussell Dahl, PhD

Elizabeth James, PhD



Learning Objectives

4 types of bonds and the properties associated with

By completing this tutorial you will learn…

properties associated with those bond types.

Bond Polarity.

Valence Bond Theory.

3/32

Concept Map

Chemistry

Studies

Previous content

New content IonicNonpolar Nonpolar C l t

Matter

Compounds

One type is

CovalentCovalent

CovalentPolar

Covalent

Metallic

4 types of bonding

4/32

ValanceBond

Theory

Most simple bonding theory



Types ofTypes of Chemical Bonds

5/32

Definition: Ionic Bond

Ionic Bond – Formed from the electrostaticattraction between positive and negativelyattraction between positive and negatively charged ions due to transfer of electrons -contains both metals and non-metals.

Na+ Cl-

6/32

A sodium atom loses an electron to form Na+ and a chlorine atom gains that electron to form Cl-. An ionic bond is formed between them.



Definition: Covalent Bond

Covalent Bond – Two non-metals share electrons to form a bond (e g CH )form a bond (e.g. CH4).

C HH

H

Sharing 4 pairs of electrons between 4xH and 1xC atoms

7/32

H

Definition: Polar Covalent Bond

Polar Covalent Bond –Two non-metals share electrons unevenly -electrons are closer to one atom than the other.

8/32

CH N



Definition: Metallic Bond

Metallic Bond – Metal atoms join together and j gpool their electrons in a large network.

Cu C

9/32

Cu Cu Cu

Cu Cu

Four Types of Bonds

Happens between

Electrons are Characteristics

The different bond types have different properties.

Metals & Non-metals

Non-metals

Transferred from one atom to another to

create ions.

Shared between 2 atoms.

High melting points, brittle, often dissolve in

water, conduct electricity when aqueous.

Low melting points, do not often dissolve in

water, do not conduct electricity when aqueous.

Ionic

Covalent

10/32

Non-Metals

Metals

Shared unevenly between 2

atoms.

Shared in a large pool with all the

atoms.

Medium melting points, sometimes dissolve in water, do not conduct

electricity when aqueous.

Soft, conductors of heat and electricity, do not

dissolve in water.

Polar Covalent

Metallic



Bond Polarity

11/32

Definition: Polar Bond

Polar Bond – uneven sharing of electrons due to differences in electronegativity (i.e. CO2).electronegativity (i.e. CO2).

The “pull” an atom has for electrons it’s sharing in a bond.

Oxygen is more electronegative than Carbon.

The Oxygen will pull on the electrons harder.The electrons will move closer to the Oxygen

This will leave the Carbonwith a partial positive charge and Oxygen with a

12/32

CO O

The electrons will move closer to the Oxygen. partial negative charge.

Note: Due to its symmetry, CO2 molecule is nonpolar. Its linear structure does not have any overall polarity because the two polar bonds cancel each other out.

δ-δ- δ+



Electronegativity Trends

Increases

In general, electronegativity:

Decreases

13/32

Common Element ElectronegativitiesHere are 8 common elements & their electronegativities.

Element Electronegativity

H 2.1

C

N

O

F

2.5

3.0

3.5

4.0

14/32

S 2.5

Cl 3.0

Br 2.8Electronegativity Mnemonic: F > O > N > Cl > Br > S > C > H = FON

(fun) Clown Brings Such CHaos.



Determining a Polar BondLook up the electronegativities for the two atoms.

Determine the (absolute value) difference in electronegativity

1

2

If there is a polar bond, indicate it with an arrow being drawn toward the more electronegative

electronegativity.

3

Differences of:0 0.4 = Non-polar covalent bond0.5 1.4 = polar covalent bond> 1.4 = ionic bond

15/32

element with a cross on the tail.

Example: Determine if each is a polar bond.C – H C = 2.5

H = 2.1Difference = 0.4Non-polar

C – N C = 2.5N = 3.0Difference = 0.5Polar

Definition: Polar Molecules

Polar Molecule – Polar bonds do not cancel out and the molecule overall has partially positive and partially negative areaspositive and partially negative areas.

O C OO

δ-

16/32

H H

Polar bonds, but non-polar molecule Polar bonds, polar molecule

δ+



Polar Molecules and Bond Geometry

δ-

The manner in which we draw a molecule could affect our determination of polarity.

O

H H

δ

δ+

OH H

17/32

It is important to know the actual 3D arrangement to determine polarity of a molecule.

δ+

Drawing water in this way makes it appear to be a non-polar molecule. Wrong!

However, water actually is shaped like this, and it is a polar molecule.

Determining Bond Types

18/32



Bond Type Flow ChartCompound

contains

Metal & Non-metal

Non-metals only

Metals only

Ionic Bonding(MgCl2)

Electronegativity difference

0 - 0.4

Electronegativity difference 0.5 – 1.4

Metallic Bonding

(Mg metal)

19/32

0 0.4 0.5 1.4

Covalent Bonding

(Cl2)

Polar Covalent Bonding

(HCl)

Determining Bond Type Example

Example: Determine the bond type of each:

K – O Metal & non-metalK O Metal & non metalIonic Bonding

C – O Non-metalsC = 2.5O = 3.5Difference = 1.0Polar Covalent

20/32

C – S Non-metalsC = 2.5S = 2.5Difference = 0Covalent



Valence Bond Theory

21/32

Definition: Valence Bond Theory

Valence Bond Theory – Bonds are formed by the orbitals of atoms overlappingby the orbitals of atoms overlapping.

Valence Bond

22/32

H HH H

s-orbitalValence Bond – A chemical bond formed by sharing valence electrons. A valence electron, for a main group element, is in the outermost electron shell. For a transition metal, it can also be in an inner shell.



Sigma & Pi Bonds

23/32

Definition: Sigma Bond - 1

Sigma Bond (σ bond) – A bond in which one pair of electrons is shared. It is formed from the overlap of 2 s-orbitals as below (head-to-the overlap of 2 s orbitals as below (head tohead overlap).

H H

24/32

2 hydrogen atoms - each has 1 electron in an s-orbital.

H Hs-orbital



Definition: Sigma Bond - 2

Sigma Bond (σ bond) – A bond in which one pair of electrons is shared. It is formed from the overlap of 2 s-orbitals as below (head-to-the overlap of 2 s orbitals as below (head tohead overlap).

H HH H

sigma bond

25/32

H H

2 hydrogen atoms - each have 1 electron in an s-orbital.As the atoms move together, their s-orbitals overlap and form a sigma bond.

H H

Definition: Pi Bond - 1Pi Bond (π bond) – 2nd or 3rd bond between two atoms. It is formed from parallel p-orbitals (side-to-side overlap).

O O

p-orbital

26/32

O Os-orbital

Only the orbitals and electrons involved in this

bond will be shown.



Definition: Pi Bond - 2Pi Bond (π bond) – 2nd or 3rd bond between two atoms. Formed from parallel p-orbitals(side-to-side overlap).

O OO O

pi bond

27/32

O OO Osigma bond

Counting Bonds

Each first bond between 2 atoms is a sigma bond.σ

How many sigma and pi bonds are in a molecule?

All 2nd and 3rd bonds between 2 atoms are pi bonds.

π

Example: Count the sigma and pi bonds in the following molecule:

H H

28/32

C C C NH

σ

π

123456

123



Diatomic and Polyatomic Compounds

The Valence Bond Theory works well for diatomic compounds (H2, O2, etc.).compounds (H2, O2, etc.).

But what about polyatomic compounds, such as CH4?

29/32

More complex theories, such as Hybridization and Molecular Orbital Theory are introduced in more advanced chemistry courses.

The type of bond can be determined from the The type of bond can

be determined from the

Learning Summary

atoms involved, and each type has common

properties.

atoms involved, and each type has common

properties.

The Valence BondThe Valence Bond

30/32

The first bond between two atoms is a σ bond, each addition bond is a

π bond.

The first bond between two atoms is a σ bond, each addition bond is a

π bond.

The Valence Bond Theory uses the

overlap of atomic orbitals for diatomic

compounds.

The Valence Bond Theory uses the

overlap of atomic orbitals for diatomic

compounds.



Congratulations

You have successfully completed the tutorial

Chemical BondingRapid Learning CenterRapid Learning Center

Rapid Learning Center

Wh t’ N t

Chemistry :: Biology :: Physics :: Math

What’s Next …

Step 1: Concepts – Core Tutorial (Just Completed)

Step 2: Practice – Interactive Problem Drill

Step 3: Recap – Super Review Cheat Sheet

32/32

Go for it!

http://www.RapidLearningCenter.com

Chemical bonding

Technology

Transcript of Chemical bonding