why does a single molecule of argon gas only contains 1 argon atom while other gases such as nitrogen contain 2 of their respective atoms?
In: Chemistry
There is no such thing as an argon molecule. Argon is an atom. Argon gas is therefore a collection of gadzillions of argon atoms, all bumping into each other but not combining with each other in any way.
A molecule is two or more atoms bonded together covalently. Covalent bonding means the atoms share electrons with each other, which creates a chemical bond that is hard to break. Electrons exist in shells around the nucleus of an atom. Inner shell, close to the nucleus, outer shell farther away. All atoms are more stable if they can find an arrangement in which they have eight electrons in their outer shell. Electrons in the outer shell participate in covalent bonding. Argon is one of the noble gases, and all noble gases have a full eight electrons in their outer shell of electrons. That is a very stable arrangement, so the atom can exist quite happily on its own, without bonding with anything else. That is why it is called a noble gas. It is able to exist all alone.
Nitrogen has only five electrons in its outer shell, but accomplishes having eight by sharing electrons with other atoms. The shared electrons create a bond between the atoms. In nitrogen gas, which is N2, each nitrogen contributes five electrons from its outer shell, making ten in all. Sharing six of these between each atom (these would be the bonding electrons, since they are shared) means that each nitrogen gets to experience eight electrons in its outer shell, hence it is a stable arrangement. That is why nitrogen gas is N2 and not N.
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