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Molecular Compounds

Molecular Compounds. Polarity. Molecular Compounds. Polarity – is the difference between the electronegativity values for the two atoms sharing a pair of electrons. The greater the difference, the more polar the bond is. Molecular Compounds.

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Molecular Compounds

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  1. Molecular Compounds Polarity

  2. Molecular Compounds • Polarity– is the difference between the electronegativity values for the two atoms sharing a pair of electrons. • The greater the difference, the more polar the bond is.

  3. Molecular Compounds • Nonpolar Covalent Bonds– this occurs when the two atoms sharing the electrons have the same electronegativity. • H2 Cl2 Br2 N2 • The electron pair is shared equally between the two atoms.

  4. Molecular Compounds • Polar Bonds - this occurs when the two atoms sharing the electrons have different electronegativity values. H-C N-O C-Cl • The electron pair is shared unequally between the two atoms. • This unequal sharing is shown by drawing an arrow towards the more electronegative atom

  5. Molecular Compounds Examples: d+ d- d+ d- C O C Cl d+ is a partial positive charge caused by the e- moving away from the atom d- is a partial negative charge caused by the e- moving toward the atom

  6. Molecular Compounds • A molecule can have polar bonds, yet still not be a polar molecule. • You must evaluate the bonds as they appear in the 3-D shape of the molecule.

  7. Molecular Compounds Example: CO2 O=C=O AX2 linear 180o Therefore, the pull of one bond cancels out the pull of the other bond. (tug-of-war; the middle doesn’t move) Each bond is polar, but the overall affect results in a nonpolar molecule

  8. Molecular Compounds • Example: CH4 H H - C - H H AX4 tetrahedral 109.5o Again, each bond is polar, yet overall, the effects cancel each other out. The molecule is nonpolar

  9. Molecular Compounds • Example: NH3 H ;; H - N - H AX3E trigonal pyramidal 109.5o Each bond is polar. In this case, the molecule is polar As the electrons are being drawn towards one end of the molecule. d- d+

  10. Molecular Compounds • It is the uneven distribution of electrons in a molecule that results in a dipole moment. • Example: • Compare the dipole moment in H2S to that of H2O

  11. Molecular Compounds H2SAX2E2 bent 109.5 H2O AX2E2 bent 109.5 • Because the H-S bond is less polar than the H-O bond, the dipole moment in H2S is weaker than the dipole moment in H2O

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