The electronegativity table is a chart of all the elements of the periodic table and their relative electronegativities. The electronegativity table was first drawn up in 1932 by the chemist Linus Pauling and gives a number to each element, the higher the electronegativity number then the higher the number of electrons which are attracted towards it. Effectively an element with a higher electronegativity number will be more likely to form a covalent bond that one with a lower electronegativity number. The most electronegative element is fluorine which has a electronegativity number of four.
There are a few electronegativity trends that can be seen by looking at the electronegativity table. As the atomic number increases along each period of the electronegativity table then so does the electronegativity number. Going down each group as the atomic number increases then electronegativity number generally decreases although there are some exceptions which result from many varying factors.
In a covalent bond between two atoms then unless they have exactly the same electronegativity (the same polarity) then a polar bond will be formed. But in a bond where they are different the pair of bonded electrons will be more attracted (closer) to one of the atoms than to the other. The effect of this is the atom that has attracted the bonded electrons becomes slightly negative and the other atom becomes slightly positive hence creating a polar bond.
There are many uses for the electronegativity table. Chemists will need to refer to it to work out the charges of atoms in a polar bond. They will also use it simply to see how likely it is that a bond will form between atoms of two certain elements. From this information chemists can work out information such as reaction rates and how much energy needs to be supplied to make a certain chemical reaction happen at a certain rate.