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Polarity. Bond Polarity & Molecular Polarity. Nonpolar Covalent Bonds. Occur when there is equal sharing of electrons between two atoms. Form between: T wo identical nonmetal atoms. Two nonmetals with electronegativity difference of 0.3 or less .
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Polarity Bond Polarity & Molecular Polarity
Nonpolar Covalent Bonds • Occur when there is equal sharing of electrons between two atoms. • Form between: • Two identicalnonmetal atoms. • Two nonmetals with electronegativity difference of 0.3 or less. • Atoms have balanced distribution of electrical charge. Nonpolar Covalent Animation
Polar Covalent Bonds • Occur when there is unequal sharing of electrons between two atoms. • Form between two differentnonmetals that have electronegativity difference between 0.3 and 1.7. • One atom will have a partial positive charge, the other will have a partial negative charge. Polar Covalent Animation
Bond Dipoles • Created by the unequal distribution of electrons in polar covalent bonds. • Electronegativity is a measure of how much an atom “hogs” electrons in a bond. • Electrons spend more time around the more electronegative atom. • Atom has a partial negative charge. • Electrons spend less time around the less electronegative atom. • Atom has a partial positive charge.
Electronegativity Values • Determined by using chart below:
Drawing Bond Dipoles • Dipoles are symbolized by: • The arrow end is placed near the partially negative atom (the more electronegative atom). • The tail end is placed near the partially positive atom (the less electronegative atom). • Electronegativity difference is used to determine if arrow is drawn or not: • Difference of 0.3 or less = NO ARROW. • Difference above 0.3 but less than 1.7 = ARROW.
Drawing Bond Dipoles • HCl • IBr • No bond dipole because electronegativity difference is less than 0.3. • N2 • No bond dipole because electronegativity difference is less than 0.3. • CO
Molecular Polarity • A molecule will be polar if: • 1. It has bond dipoles. • 2. The bond dipoles are unequally distributed. • Draw dipoles on the molecules below and determine if they are polar or nonpolar.
Molecular Polarity • Answers: • Water is polar. • Ammonia is polar. • Carbon tetrachloride is nonpolar. • Carbon dioxide is nonpolar.