Polar Molecular Compounds
description
Transcript of Polar Molecular Compounds
Polar Molecular CompoundsSWBAT: Identify Polar and Nonpolar Molecules
Periodic Table TrendsAtomic Radii
Half the distance between the nuclei of two adjacent atoms
Electronegativity
Ability of an atom to attract electrons when bonded with another atom
Atomic Radii Trend
Atomic Radii Trend
Electronegativity Trend Electronegativity is highest within the
nonmetals with Fluorine having the highest. Why are noble gases excluded?
Electronegativity Trend
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
Electronegativity Differenceand type of bond
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
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
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
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
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
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
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
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