Compounds are different from elements primarily because compounds are composed of one or two elements. In this case, when elements are combined to form a compound,the reaction incurs a chemical change which results to a product with different properties as its base elements.
Types of Bonds can be predicted by calculating the
difference in electronegativity.
If, Electronegativity difference is,
Less
than 0.4 then it is Non Polar Covalent Bond
Between 0.4 and 1.7 then it is Polar Covalent Bond
Greater than 1.7 then it is Ionic
For N and Se,
E.N of Nitrogen = 3.04
E.N of Selenium = 2.55
________
E.N Difference
0.49 (Weakly Polar Covalent)
As you have not provided remaining pairs, so if you have any of them, follow the method as mentioned above.
A polar molecule is a molecule whose ends have opposite electric charges. An example of a polar molecule is H2O or water. Water has 1 side which is positive and the other side which is negative. It is a dipole which means that the two sides are not having the same charges.