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Polarity

Polarity. Y12 Chemistry. Polarity. Having poles Opposite ends In molecules its respect to charge Covalent bonds can be either polar or non-polar. Electronegativity. The ability of an atom to attract bonding electrons to itself. Electronegativity. Every atom is neutral….

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Polarity

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  1. Polarity Y12 Chemistry

  2. Polarity • Having poles • Opposite ends • In molecules its respect to charge • Covalent bonds can be either polar or non-polar

  3. Electronegativity The ability of an atom to attract bonding electrons to itself

  4. Electronegativity • Every atom is neutral…. • But the positive nucleus attracts bonding electrons depending on; • The amount of positive charge on the nucleus of the atom • The radius of the atom

  5. Electronegativities Increase across a period Flourine has the highest electronegativity Increase up a group

  6. Polar Bonds • Occur because the more electronegative atom has a greater “pull” on the bonded electrons • This leads to a slightly negative charge • The other atom is slightly positive + H Cl

  7. Ionic Covalent Continuum • Calculating the electronegativity difference between two atoms will tell us if a bond is ionic, polar covalent or non polar covalent. <0.5 0.5 – 1.6 >1.6 Ionic Non polar covalent Polar covalent

  8. Dipoles • A bond which has a positive end and a negative end is said to have an electrical dipole • The direction of the dipole is from positive to negative H Cl

  9. Polar molecules • Many molecules contain more than one bond • Each bond may or may not be polar • Sometimes the dipoles will be balanced and sometimes they will form a net dipole in one direction • A molecule with a net dipole is a polar molecule

  10. Predicting polarity • Molecules with one bond are easy • If the bond is polar the molecule is polar H Cl

  11. Predicting Polarity • In molecules with more than two atoms and polar bonds, the molecule will be non-polar only if the polarities of the bonds cancel each other out C O O CO2 is non polar because the shape is symmetrical so the polar bonds cancel each other out

  12. Predicting Polarity

  13. Symmetry of shapes

  14. CCl4 • 4 C – Cl bonds • All C  Cl

  15. CHCl3 • 3 C – Cl bonds and 1 C - H • 3 C  Cl and 1 C  H

  16. NH3 • 3 N – H bonds • All N  H

  17. Construct a flow-chart to identify polar molecules using the following statements: Polar Bonds Non-polar bonds Bonded non-metal atoms identical Bonded non-metal atoms different Electronegativity difference No electronegativity difference Polar molecule Non-polar molecule Net dipole Polar bonds cancel Polar bonds don’t cancel Polar bonds asymmetrically arranged Polar bonds symmetrically arranged

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