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High School Chemistry Rapid Learning Series - 15
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Rapid Learning CenterChemistry :: Biology :: Physics :: Math
Rapid Learning Center Presents …p g
Teach Yourself High School Chemistry in 24 Hours
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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
High School Chemistry Rapid Learning Series - 15
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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.
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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
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ValanceBond
Theory
Most simple bonding theory
High School Chemistry Rapid Learning Series - 15
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Types ofTypes of Chemical Bonds
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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-
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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.
High School Chemistry Rapid Learning Series - 15
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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
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H
Definition: Polar Covalent Bond
Polar Covalent Bond –Two non-metals share electrons unevenly -electrons are closer to one atom than the other.
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CH N
High School Chemistry Rapid Learning Series - 15
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Definition: Metallic Bond
Metallic Bond – Metal atoms join together and j gpool their electrons in a large network.
Cu C
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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
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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
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Bond Polarity
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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
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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+
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Electronegativity Trends
Increases
In general, electronegativity:
Decreases
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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
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S 2.5
Cl 3.0
Br 2.8Electronegativity Mnemonic: F > O > N > Cl > Br > S > C > H = FON
(fun) Clown Brings Such CHaos.
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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
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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-
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H H
Polar bonds, but non-polar molecule Polar bonds, polar molecule
δ+
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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
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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
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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)
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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
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C – S Non-metalsC = 2.5S = 2.5Difference = 0Covalent
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Valence Bond Theory
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Definition: Valence Bond Theory
Valence Bond Theory – Bonds are formed by the orbitals of atoms overlappingby the orbitals of atoms overlapping.
Valence Bond
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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.
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Sigma & Pi Bonds
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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
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2 hydrogen atoms - each has 1 electron in an s-orbital.
H Hs-orbital
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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
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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
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O Os-orbital
Only the orbitals and electrons involved in this
bond will be shown.
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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
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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
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C C C NH
σ
π
123456
123
High School Chemistry Rapid Learning Series - 15
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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?
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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
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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.
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