Why is NH3 polar
What is NH3?
NH3 is the chemical name or rather the chemical formula for Ammonia, where N stands for Nitrogen and H stands for Hydrogen. NH3 is a compound of Nitrogen and Hydrogen where one atom of Nitrogen and three atoms of Hydrogen combine together to give two molecules of Ammonia. The following equation should elaborate on the origin of the chemical formula NH3.
N2 + 3h2 —-> 2NH3
Ammonia in General
Ammonia in its natural form is a colorless gas but it’s certainly not odorless; in fact, it has a characteristic pungent smell that is similar to the odor of rotten eggs. It is among one of the most commonly manufactured and utilized industrial chemicals today although, it is also naturally occurring in animals, plants and also is a part of the nitrogen cycle (bacterial processing). In most land animals, ammonia is an essential precursor that helps in the synthesis of amino acid and nucleotides.
While there are other uses of ammonia, most (about 80%) of the industrially manufactured ammonia is used for fertilization purposes. Other uses of ammonia include its applications as a refrigerant and water purifying agent. Ammonia is also an important component while making explosives, other chemicals, colors and even pesticides. Due to its strong alkaline nature, ammonia is used both in industrial as well as in household cleaners.
Why is it Polar?
There are certain criterions that each chemical must fulfill in order to be considered polar and since ammonia passes those criterions, it falls among the list of polar chemicals on earth. Primarily though, one can consider that the polarity of ammonia is due to the fact that its nitrogen atom has only one single pair of electrons with it.
Now, a question might occur that how is ammonia polar when it has a covalent bond? To answer this, one might take the example of the bonding between a fluorine atom and a carbon atom. While ideally, the electrons should be exactly in the middle of the two bonding atoms, that is not what would happen in this particular example because fluorine, in addition to being the smaller atom, has more protons and thus the electrons will be closer to the fluorine atom than the carbon atom. This is an unequal sharing of electrons between two bonded atoms and such bonds are known as polar bonds. The bond between the nitrogen and the hydrogen atoms are also similar in case of ammonia.
According to the Lewis structure, the diagram of the bonding clearly shows that one nitrogen atom is bonded to three hydrogen atoms and it also is leaving a single pair of nitrogen electrons unshared or free.
In the typical bonding between nitrogen and hydrogen that occurs when ammonia is formed, the two elements associated exhibit different electronegativity. Hydrogen is found to be positively charged while nitrogen is found to be negatively charged and the single lone pair of electrons (valence) of the nitrogen atom is also there. If the lone pair of valence electrons were not there, the opposite charges of the two types of atoms would cancel each other out; but it cannot be so as they ARE there. This of course is why a polar molecule is created each time when a molecule of ammonia is formed.