Question

Which of these are polar or are none of them polar?

• NH4+
• SiCl4
• Cl2O

Answer 1

First, you need to determine the shape of these molecules. You do this by finding out how many pairs of electrons are around the central atom. In the 1st two, there are 4 bonding pairs of electrons around the central atom. The last one is a little different because there are 2 bonding pairs and 2 lone pairs of electrons. From using the greatest distance between the electron pairs you can determine that the shape of the molecules will be tetrahedral. For the first 2, all the atoms around the central atom are the same. This normally means that the molecule is nonpolar so that SiCl4 is a nonpolar molecule. The NH4+ should also be nonpolar but it is due to the positive charge. The Cl2O molecule as the atom unequally distributed around the center atom so that this is a polar molecule.
In order to have a polar molecule, there must be an unequal distribution of the negatively charged electrons in the orbit of the molecule. The dipoles are unequally charged either because of the net electronegativity of the molecule or by the shape of the molecule causing the negative dipole.