IIIIIIIV Ch. 9 – Chemical Names and Formulas I. Ion Formation Ionic Formulas Ionic Nomenclature.
IIIIIIIV Chemical Bonding Chapter 6 Section 1 & 2 Pages 175-189.
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Transcript of IIIIIIIV Chemical Bonding Chapter 6 Section 1 & 2 Pages 175-189.
![Page 1: IIIIIIIV Chemical Bonding Chapter 6 Section 1 & 2 Pages 175-189.](https://reader036.fdocuments.in/reader036/viewer/2022062413/5a4d1b467f8b9ab0599a3984/html5/thumbnails/1.jpg)
I II III IV
Chemical Bonding
Chapter 6
Section 1 & 2
Pages 175-189
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Chemical Bond Attractive force between atoms or
ions that binds them together as a unit.(valence e- of one atom attracted to the nucleus of another atom).
Bonds tend to form to decrease potential energy or increase
stability. Types are ionic or covalent.
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Ionic Bond
A cation is attracted to an anion• Cation = positively
charged ion• Anion = negatively
charged ion
Octet Rule is followed!
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Ionic Compounds
Tend to form a crystal lattice.
Highly ordered
Repeating pattern
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Ionic Compound metal-nonmetal
Two or more elements are combined in a chemical bond by gaining or losing electrons that achieves the octet rule.
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Covalent Bonding nonmetal-nonmetal
A covalent bond is formed by a shared pair of electrons between two atoms.
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ElectronegativityUsing Electronegativity values one can determine
the % ionic character.Nonpolar-covalent, equal sharing of electrons.
Bonds having 0% to 5% ionic character. Electronegativity differences of 0 to 0.3.
Polar-covalent, unequal sharing of electrons. Bonds having 5% to 50% ionic character. Electronegativity differences between 0.3 to 1.7.
Ionic bonding, is a complete transfer of electrons. >50% ionic character. Electronegativity differences of 1.7 to 3.3
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Molecule; nonmetal-nonmetal
A group of atoms united by covalent bonds. ( polar or non-polar covalent).
Diatomic Molecule
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Molecular Substances
Substance made of molecules
DNA
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*The law of Octet
Octet Rule:
Atoms tend to gain, lose, or share electrons in order to get a full set of valence electrons.
(usually 8 electrons)
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Bond Length
Increases as you go down a group, because the atomic radius increases.
Shorter for multiple bonds.
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Multiple Bond LengthTriple bond is shorter than double bond, which is shorter than single bond.
Why? The more electrons in a bond, the stronger the attraction to the positively charged nuclei of the bonding atoms.
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Bond Energies KJ/molBond Energies- The amount of energy
required to break a chemical bond and form neutral isolated atoms.
In general the higher the bond energy required the stronger the attraction, the shorter the chemical bond. (Data table on page 182)
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Exceptions to the Octet Rule
Exceptions are those that form bonds that either have less than 8e- or more than 8e-
Less than eight:
Hydrogen can form one bond that has 2e-
Boron forms three bonds that contains 6e-
More than eight:
Sulfur can form 6 bonds containing 12e-
Phosphorus can form 5 bonds containing 10e-
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Lewis Dot Diagrams
Lewis Structures
The use of dots or other symbols to represent bonded and unshared electrons.
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2 shared electronsmake a bond.
Lines show the bond between atoms in a compound.
Structural (lines= 2e- )
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How to Draw Lewis Structures:
Step 1 (N) determine the number of electrons Needed for each atom in the compound. Grp’s 14,15,16,17 all need 8. Hydrogen needs 2.
Step 2 (A)determine the number of electrons Available, which is determined by the grp # .
Step 3 N – A = e- Shared (S)
Step 4 A - S = Unshared (U)
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Example: Methane CH4
4(2) + 1(8) = 16e-
Step 1 = Electrons Needed N
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CCarbon goes in the middle because it is the singular atom.
Step 2 = Electrons Available A
1(4) + 4(1) = 8e-
HH
HH
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C
Bonds go between atoms
Each bond uses up 2 electrons
Step 2 = N – A = S
16 – 8 = 8e- Shared
HH
HH
4 Bonds use up 8 electrons (4 x 2 = 8)Unshared ? 8 – 8 = 0
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Step 1 determine NStep 2 determine AStep 3 N – A = SStep 4 A – S = U
Step 1: Ammonia NH3
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NNitrogen goes in the middle because it is the singular atom.
Arrange Atoms
HH
H
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N
Bonds go between atoms (6e-)
Each bond uses up 2 e-
Step 2:Form Bonds
HH
H
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N
N = 14 A = 8 S = 6 A – S = 2 Used up 6e- with bonds
2 unshared to complete the
octet You’re done!
complete the octet
HH
H••
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Step 1 NStep 2 AStep 3 N – A = SStep 4 A – S = U
Example Formaldehyde CH2O
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CYou would have to guess whether C or O goes in the middle?It is Carbon, because it can form the most bonds, and least electronegative!
Arrange Atoms
HH
O
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C
Bonds go between atoms
Each bond uses up 2 electrons
Form Bonds
HH
O
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C
Had total of 20e- from step 1 Used up 6e- with bonds Need 2 more e- on C Need 6 more e- on O NOT ENOUGH TO GO AROUND
NEED DOUBLE BOND.
Step 3:Distribute remaining electrons
HH
O
Need 2 more e- on carbon to complete octet!
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C
Remember the Octet
Rule ! Carbon & Oxygen both
need 8e-. They get 8 by sharing 4
e- between them.
Double Bonds
HH
O••
••••
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C Represent double bond
with a double line. You are done!
Double Bonds
HH
O••
••
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Double bonds occur in these
molecular compounds;
Oxygen, Carbon Dioxide
Triple Bonds: Nitrogen
Multiple Bonds
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Resonance StructuresMolecules that can’t be correctly
represented by a single Lewis diagram.Actual structure is an average of all the
possibilities.Show possible structures separated by a
double-headed arrow.
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Example: SO3
OO S O
OO S O
OO S O