lesson 1 intro to chemical bonding
DESCRIPTION
Covalent Bonding Unit Lesson 1 Intro to BondingTRANSCRIPT
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Covalent Bonding Unit
Lesson 1: Introduction to Chemical Bonding
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TargetsI can define chemical bond.I can describe covalent bonding.I can classify bonding type
according to electronegativity differences.
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DefinitionsChemical Bond – mutual electrical
attraction between the nuclei and valence electrons of different atoms that bind the atoms together
Valence electrons – outermost electrons that are available to be lost, gained, or shared to form a chemical bond
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Chemical Bond
A force that holds groups of 2 or more atoms together and makes them function as a unitAtom – smallest unit of an elementMolecule – Group of covalently bonded
atomsAtoms
Molecule
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Types of Chemical BondsIonic Bonding – (covered in next chapter)
a type of bond in which a metal and a nonmetal transfer electrons
Covalent Bonding – type of bond in which 2 or more nonmetal atoms share electrons
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Periodic TableIONIC – Metal + nonmetalCOVALENT – 2 nonmetals
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Types of Covalent BondsNonpolar covalent bond – electrons are
shared equally
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Types of Chemical BondsPolar covalent – electrons are not shared
equally because one atom attracts the shared electrons more than the other atom
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Bond Types Video
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Electronegativity
Electronegativity - measure of an atom’s ability to attract electrons.
Electronegativities tend to increase across a period and decrease down a group
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Classifying Chemical BondsThe polarity of a bond depends on the
difference between the electronegativity values of the atoms forming the bonds.
Nonpolar covalent – 0 to 0.3Polar covalent – 0.4 to 1.7Ionic – greater than 1.8
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Increases from left to right across a period Decreases down a group of representative
elements
Electronegativity Values
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PracticeUse electronegativity values to classify the
following bonds:a. Sulfur and Hydrogenb. Lithium and Fluorinec. Potassium and Chlorined. Iodine and Brominee. Carbon and Hydrogen
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PracticeUse electronegativity values to classify the
following bonds:a. Sulfur and Hydrogen 2.5 – 2.1 = 0.4;
polar covalentb. Lithium and Fluorine 4.0 – 1.0 = 3.0;
Ionicc. Potassium and Chlorine 3.0 – 0.8 =
2.2; Ionicd. Iodine and Bromine 2.8 – 2.5 = 0.3;
Nonpolar covalente. Carbon and Hydrogen 2.5 – 2.1 = 0.4 ;
polar covalent
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Covalent Bonding and Molecular Compounds
Covalent Bonding
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TargetsI can explain why most atoms form
chemical bonds.I can explain the relationships among
potential energy, distance between approaching atoms, bond length and bond energy.
I can state the octet rule.I can determine the number of valence
electrons for a given atom.
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Nature favors chemical bonding because most atoms have lower potential energy when they are bonded to other atoms.
Formation of a Covalent Bond
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Each atom has a positive nucleus in the center and negative electrons surrounding the nucleus in a spherical pattern.
The positively charged nuclei are attracted to the negatively charged electrons.
Formation of a Covalent Bond
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As the atoms approach each other, the charged particles interact: nucleus on one atom attracts electrons on the other atom.
Formation of a Covalent Bond
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As the atoms approach one another, the potential energy decreases.
A bond forms when the potential energy is at a minimum.
Formation of a Covalent Bond
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If the atoms continue to approach one another once the bond forms, the nuclei will begin to repel one another and the potential energy will start to increase.
Formation of a Covalent Bond
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Characteristics of the Covalent Bond
Bond length – distance between two bonded atoms at their minimum potential energy or the average distance between two bonded atoms
Bond energy – energy required to break a chemical bond and form neutral isolated atoms
- kilojoules per mole (kJ/mol)Bond lengths and bond energies vary with
the types of atoms that have combined
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The octet rule states that atoms tend to lose, gain or share electrons until they are surrounded by 8 electrons in their valence shell.
The number of valence electrons is equal to the group number. (Groups 13-18; Group # -10)
LABEL YOUR PERIODIC TABLE
The Octet Rule
1A2A 3A4A5A6A7A
8A
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PracticeWhat is the relationship between bond
energy and bond length?
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PracticeWhat is the relationship between bond
energy and bond length? The bond length decreases as the
strength of the bond increases.
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PracticeArrange the following in order of increasing
bond strength: C–Cl, C–I, H–F, and I–ISKIP
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PracticeArrange the following in order of increasing
bond strength: C–Cl, C–I, H–F, and I–II-I, C-I, C-Cl, H-F
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Which pair of bonded atoms has the strongest bond?
Practice Problems
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Which pair of bonded atoms has the strongest bond?H – F
Practice Problems
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Which pair of bonded atoms has the weakest bond?
Practice Problems
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Which pair of bonded atoms has the weakest bond?I – I
Practice Problems
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Arrange the following bond lengths in order of increasing bond strength: 72 pm, 149 pm, 53 pm, and 398 pm
SKIP
Practice Problems
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Arrange the following bond lengths in order of increasing bond strength: 72 pm, 149 pm, 53 pm, and 398 pm 398 pm, 149 pm, 72 pm, 53 pm
Practice Problems
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Determine the number of valence electrons in each of the following atoms.LithiumSulfurCarbonNeon
Practice Problems
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Determine the number of valence electrons in each of the following atoms.Lithium - 1Sulfur - 6Carbon -4Neon - 8
Practice Problems