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Explore why bonding is crucial in chemistry, defining substance properties. Learn about electronegativity, polar vs. nonpolar covalent bonds, and ionic bonds. Calculate bond types and see Lewis structures with examples.
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Introduction to Bonding and electron dot/lewis structures Chemistry
Why is bonding important?? • Without bonding the universe would be a mass of individual atoms. • The type of bond defines the properties of a substance. • NaCl…shape • H2O and oil…dissolving
Electronegativity • Ability of atoms within a molecule to attract electrons
Polar • Describes molecules with an unequal distribution of electrons • (nonpolar = equal)
Covalent • Describes a bond where electrons are shared
Ionic • Describes a bond where electrons are transferred
DETERMINING BOND TYPE • Calculate the difference in electronegativities: > 1.7 = ionic (electrons transfer) 0.3-1.7 = polar covalent (electrons are shared unequally) <0.3 = nonpolar covalent (equal sharing of electrons)
EXAMPLE: 1. H2 a) Calculate the difference in electronegativities: 2.2 – 2.2 = 0 nonpolar covalent (equal sharing) b) Draw the electron dot/Lewis structure: H + H = H H [recall the “duet rule”—H wants 2 e-]
Nonpolar Covalent Bonds • Describes a bond where electrons are shared equally • Less than 0.3 electronegativity difference. • Let’s look at an animation of this with H2: H2 EN=0 (http://www2.gasou.edu/chemdept/general/molecule/polar.htm) (http://web.jjay.cuny.edu/~acarpi/NSC/5-bonds.htm)
EXAMPLE: 2. H2O a) calculate the difference in electronegativities: 3.5 – 2.2 = 1.3 polar covalent (unequal sharing) b) Draw the electron dot/Lewis structure: H + H + O = H O H [recall the “duet rule”—H wants 2 e-]
Polar Covalent Bonds • Describes a bond where electrons are shared unequally • Electronegativity (EN) difference is between 0.3 and 1.7. • Let’s look at an animation of this with H2O and HBr: H2O END=1.4 HBr END=0.7 (http://www2.gasou.edu/chemdept/general/molecule/polar.htm) (http://web.jjay.cuny.edu/~acarpi/NSC/5-bonds.htm)
EXAMPLE: 3. HF a) calculate the difference in electronegativities: 4.0 – 2.2 = 1.8 ionic (electrons are transferred) b) Draw the electron dot/Lewis structure: H + F = H F - +
Ionic Bonds • Describes a bond where electrons are transferred. • Greater than 1.7 electronegativity difference. • Let’s look at an example of this with NaCl: NaCl EN=2.1 (http://www2.gasou.edu/chemdept/general/molecule/polar.htm) (http://web.jjay.cuny.edu/~acarpi/NSC/5-bonds.htm)