(Polar molecules, Non-polar molecules, etc.)
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I don't think we need to memorize exact electronegativities, but knowing the trends in electronegativity would probably be helpful to determine what bonds would be polar vs nonpolar. In general, the electronegativity increases as you move diagonally up and to the right of the periodic table.
I don't think we need to know exact values, but we should know generally which atom is the most electronegative in relation to others in the molecule.
We're not expected to know the exact electronegativity values, instead we should know the periodic trend for electronegativity which follows the same trends as ionization energy and electron affinity. Also, the questions we'll be given will probably make the electronegativity differences between two atoms be obvious from the trends which will help us find the dipole moment.
I don't think we have to know exact values of electronegativity. However, the periodic table should tell us the polarity (or lack thereof) of molecules based on the trends of electronegativity.
We don't have to determine polarity of the molecule using exact electronegativity values. We can determine if a bond is polar/nonpolar using trends from the periodic table. If polar bonds cause dipoles and don't cancel out in a molecule, it will be polar. If the dipoles do cancel out, the molecule will be nonpolar.
I don't think it will be necessary to know specific electronegativity numbers, but there are some cases in which you can use the the trends of electronegativity to determine if the molecule has a net dipole moment. If it does, it will be polar. If not then it will be non polar.
when determining the polarity we only need to take into account the electronegativity trends in the periodic table, therefore, don't need to memorize exact values.
We don't have to memorize the electronegativity chart. It's easier to use the net dipole to figure out if the molecule is polar or not. For example, for CH3Cl, there is a net dipole towards the chlorine atom, making the whole molecule. However, for CH4, there is no net dipole which makes the molecule non polar.
When determining if a molecule is polar or non polar on the test, it is not expected of us to know the electronegativity values of the elements in the given molecules. Just know the periodic trends for electronegativity and you should be fine.
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