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Covalent Bonding Unit Lesson 1 Intro to Bonding
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Covalent Bonding Unit
Lesson 1: Introduction to Chemical Bonding
TargetsI can define chemical bond.I can describe covalent bonding.I can classify bonding type
according to electronegativity differences.
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
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
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
Periodic TableIONIC – Metal + nonmetalCOVALENT – 2 nonmetals
Types of Covalent BondsNonpolar covalent bond – electrons are
shared equally
Types of Chemical BondsPolar covalent – electrons are not shared
equally because one atom attracts the shared electrons more than the other atom
Bond Types Video
Electronegativity
Electronegativity - measure of an atom’s ability to attract electrons.
Electronegativities tend to increase across a period and decrease down a group
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
Increases from left to right across a period Decreases down a group of representative
elements
Electronegativity Values
PracticeUse electronegativity values to classify the
following bonds:a. Sulfur and Hydrogenb. Lithium and Fluorinec. Potassium and Chlorined. Iodine and Brominee. Carbon and Hydrogen
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
Covalent Bonding and Molecular Compounds
Covalent Bonding
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.
Nature favors chemical bonding because most atoms have lower potential energy when they are bonded to other atoms.
Formation of a Covalent Bond
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
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
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
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
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
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
PracticeWhat is the relationship between bond
energy and bond length?
PracticeWhat is the relationship between bond
energy and bond length? The bond length decreases as the
strength of the bond increases.
PracticeArrange the following in order of increasing
bond strength: C–Cl, C–I, H–F, and I–ISKIP
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
Which pair of bonded atoms has the strongest bond?
Practice Problems
Which pair of bonded atoms has the strongest bond?H – F
Practice Problems
Which pair of bonded atoms has the weakest bond?
Practice Problems
Which pair of bonded atoms has the weakest bond?I – I
Practice Problems
Arrange the following bond lengths in order of increasing bond strength: 72 pm, 149 pm, 53 pm, and 398 pm
SKIP
Practice Problems
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
Determine the number of valence electrons in each of the following atoms.LithiumSulfurCarbonNeon
Practice Problems
Determine the number of valence electrons in each of the following atoms.Lithium - 1Sulfur - 6Carbon -4Neon - 8
Practice Problems
