Polar Molecular Compounds SWBAT: Identify Polar and Nonpolar Molecules.
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Transcript of Polar Molecular Compounds SWBAT: Identify Polar and Nonpolar Molecules.
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Polar Molecular CompoundsSWBAT: Identify Polar and Nonpolar Molecules
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Periodic Table Trends
Atomic Radii Half the distance
between the nuclei of two adjacent atoms
Electronegativity
Ability of an atom to attract electrons when bonded with another atom
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Atomic Radii Trend
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Atomic Radii Trend
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Electronegativity Trend Electronegativity is highest within the
nonmetals with Fluorine having the highest. Why are noble gases excluded?
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Electronegativity Trend
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A. Three Types of Bonds: non-polar, polar, ionic
Use Electronegativity (EN) values to determine type of bondEN value:
H = 2.1 C = 2.5 N = 3.0 O = 3.5 F = 4.0 P = 2.1 S = 2.5 Cl = 3.0
Br = 2.8 I = 2.5
Every element has a specific EN valueWe will focus on the elements of organic chemistry C,H,N,O,P,S and HalogensDo not need to memorize
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Electronegativity Differenceand type of bond
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Rating of Covalent Bonds:
Example 1: What type of bond is H-Cl? EN: H = 2.1 Cl: 3.0 Subtract ENs from each other, larger – smaller 3.0 – 2.1 = 0.9 compare to rating Redraw compound with partial charges: δ+ &
δ- δ+ δ-
H – Cl Dipole Moment
0 - .4 = nonpolar.5 – 1.7 = polar1.8 and greater = ionic
*Polar Covalent
0 - .4 = nonpolar.5 – 1.7 = polar1.8 and greater = ionic
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Rating of Covalent Bonds:
Example 1: What type of bond is H-Br? EN: H = 2.1 Br: 2.8 Subtract ENs from each other, larger – smaller 2.8 – 2.1 = 0.7 compare to rating Redraw compound with partial charges: δ+ &
δ- δ+ δ-
H – Br Dipole Moment
0 - .4 = nonpolar.5 – 1.7 = polar1.8 and greater = ionic
*Polar Covalent
0 - .4 = nonpolar.5 – 1.7 = polar1.8 and greater = ionic
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Rating of Covalent Bonds:
Example 2: What type of bond is C-H? EN: H = 2.1 C: 2.5 Subtract ENs from each other, larger – smaller 2.5 – 2.1 = 0.4 compare to rating Less than 0.5 = no partial charges, no dipole
arrow
C – H
0 - .4 = nonpolar.5 – 1.7 = polar1.8 and greater = ionic
*Nonpolar Covalent
0 - .4 = nonpolar.5 – 1.7 = polar1.8 and greater = ionic
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Tips Bonds between different elements
always have some kind of dipole moment regardless of polarity rating
Draw the dipole arrow of Br – Pd (use just their position in the PT)
Br – Pd Bonds between same elements never
have a dipole moment regardless of individual EN
No dipole between F – F or H – H
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Practice Problems Using electronegativity difference,
classify each bond as ionic, polar covalent, or nonpolar covalent. Show the partial charge for any polar
covalent bonds.
K – F EN values: K = 0.8 & F = 4.0 O – O EN values: O = 3.5 I – Cl EN values: I = 2.5, & Cl = 3.0
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Practice Problems Using electronegativity difference, classify
each bond as ionic, polar covalent, or nonpolar covalent. Show the partial charge for any polar
covalent bonds. K – F EN values: K = 0.8 & F = 4.0
4.0 - 0.8 = 3.2 - ionic bond O – O EN values: O = 3.5
3.5 - 3.5 = 0 - nonpolar covalent bond I – Cl EN values: I = 2.5 & Cl = 3.0
3.0 - 2.5 = 0.5 - polar covalent bond δ+
δ-
I – Cl
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Practice Problems The bonds between the following pairs
of elements are covalent. Arrange them according to polarity, listing the most polar first.a. H – Cl b. H – C c. H – Fd. H – O e. H – H f. S – Cl
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Homework Problems 4.50 Describe the end in EN going down a
group. 4.52 Approximately what EN difference would
you expect for a polar covalent bond? 4.54 Predict whether each of the following
bonds is ionic, polar covalent or nonpolar covalent: A. Si-O B. K-Cl C. S-F D. P-Br E. Li-O F. N-
P 4.56 For each of the following bonds, indicate
the positive end with δ+ and the negative end with δ-. Write an arrow to show the dipole for each. A. Si-Br B. Se-F C. Br-F D. N-H E. N-P