Polar & non-polar covalent bonds Mostly covalent animations

Covalent bonding (expectation 7) Which will gain or lose? Why? When electronegativity values are high, each atom fights to keep the electrons. In this case, atoms share electrons to satisfy the octet rule. A covalent bond is when atoms share electrons & stay together because both have ownership over the electrons.

Electronegativity & bond type (expectation 9) The attraction to a bonding electron The difference in electronegativity decides the type of bond. Ionic bond: Difference is > 2.0 (between metals & non-metals) & results in ions due to electron transfer. Polar covalent: Difference is > 0.4 but < 2.0 & results in unequal sharing Non-polar covalent: difference is < 0.4 & allows equal sharing

Non- polar bonds (Expectation 9) Small or no difference in electronegativity Shared pair of electrons is shared equally by each atom. Shared electrons are equally between each atom No partial charges exist Eg. F – F Cl - Br

Polar bonds (expectation 9) The shared electrons are closer to one atom than the other so are not in the middle. The more electronegative atom wins. The atom with greater electronegativity pulls the shared electrons closer to it. Eg. C-F Which has a stronger “pull” on the electrons? The F atom is slightly negative because the electrons are closer to F. The C atom is slightly positive because the electrons are farther from C. Unequal sharing of electrons produces partial charges in a molecule (poles).

Polarity (Expectation 10) Polarity exists if a molecule has charged poles (opposite ends) due to electronegativity differences These molecules are attracted to other molecules with a charge. The more similar the polarities are the easier the two substances mix.

Polarity & shape A molecule can have polar bonds & be a polar molecule. Eg. Which atom is sort of negative & sort of positive?  S-O H-Cl C-O  A molecule can have a polar bond & NOT be a polar molecule.  Eg. CO2 looks like O-C-O  Both oxygens pull equally & cancel each other out so there is no polar end.  The shape of a molecule can affect whether a molecule is polar. Polar bonds can cancel each other out.

Memorize Salt (NaCl) is ionic. Water is polar. Oil is non-polar. Ionic compounds (salt) can dissolve in polar substances (water).

Ionics dissolve in water The polarity of water explains the fact that ionic compounds dissolve in water. The charges of the ions in the ionic bond are attracted to the polar ends of water (the “sort of” negative & “sort of” positive charges).

Ionic Large electronegativity difference results in one atom taking the electron. MgO Oxygen’s has a high electronegativity & Mg is low. Bonding electron distribution Mg is + & O is – so they stick together