Polarity Due To Electronegativity
- · all the atoms of the periodic table have a certain ability to attract electrons of other atoms – this ability is called electronegativity
- · atoms on the right upper hand corner of the periodic table are the smallest, and as a result, their positive proton can get close to electrons of other atoms to attract them away from the other atom and bring them over to themselves – this means that these atoms have a high electronegativity
- · atoms on the lower left hand corner of the periodic table are the largest, therefore have a low electronegativity
- · when two or more atoms combine, the greater their difference in electronegativity, the greater the polarity of that substance
- · in all cases of ionic bonding, and in some cases of covalent bonding where sharing of the electron pair is not equal, the molecule results in being polar - it has a positive end and a negative end
- · this is because the electrons spend more time around one species (the more electronegative one), and less time around another (the less electronegative one)
- · this means that each end of the molecule is oppositely charged – one end is slightly positive, the other, slightly negative
- · to determine the amount of polarity in a molecule, the electronegativity values of the atoms involved are subtracted from one another
- · if the difference is less than 1.7, the molecule is said to be a polar covalent substance
- · if the difference in electronegativity greater than 1.7, the molecule is said to be ionic in character
- · for example, hydrogen chloride is more polar than chlorine gas because the difference in electronegativity between hydrogen and chlorine is 2.9 – 2.1 = 0.8, and the difference between the two atoms of chlorine in chlorine gas is 2.9 – 2.9 = 0.0.
- · hydrogen chloride is slightly polar, and chlorine gas is completely non-polar (the truest molecule you can get)
