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
The simplest answer is because it is more stable that way. Atoms in molecules generally want to form an outside layer of 8 electrons (or 2 for hydrogen, since there are only 2). Although it’s a different process, this is the same idea behind Na giving an electron to Cl to form Na+ and Cl- that bond.
H has 1 outer electron and bonds covalently with another H, so they share 2 electrons, which they like.
N has 5 outer electrons and forms a triple bond with another N, so they share 8 outer electrons, which they like.
O has 6 outer electrons and forms a double bond with another O, so they share 8 outer electrons, which they like.
The remaining elements that bond like this (F, Cl, Br, and I) have 7 outer electrons and form a single bond with a similar element, so they share 8 outer electrons, which they like.
The 7 elements that form these diatomic elements are H, N, O, F, Cl, Br, and I. Sometime a mnemonic like “Mr. BrINClHOF” is used. I’ve also hear “Hydrogen and the 7” because there are 7 total; other than hydrogen, it starts with element #7, N; and the shape of the elements other than H looks like a 7 on the periodic table.
Noble gases are inert, non-reactive, because the outer shell is full ( electrons don’t interact with the electrons in other molecules ). https://en.m.wikipedia.org/wiki/Noble_gas
Atoms like to be stable. This stability has to do with having the right amount of electrons to “balance” things. Argon, and other similar gasses, have a perfect amount of electrons to be nice and balanced. Most other elements don’t, so they combine with others to share electrons and be nice and balanced.
This has nothing to do with them being gases, really.
It’s simply a matter of the chemical properties of the atom. Some atoms want to make connections, and others are perfectly happy alone. It has to do with the number of outer electrons they have: if their outer electrons are “full” they don’t connect to anything, but if any are missing they try to connect with other atoms to complete them.
For a lot of atoms, the easiest thing to connect to is other copies of themselves. And if you were to isolate a lot of that single element, it would have no choice but to bond with itself because it hates being alone that much.
Argon is a noble gas, which is a group of elements that have “full” electron shells and don’t care about connecting to anything else. That’s basically it.
Atoms have different numbers of electrons in “shells” around their central nucellus. The first shell has a maximum of 2 electrons, then every shell after that has a maximum of 8. When atoms come together to form molecules, they like to share electrons to form 8, that’s what makes for the most stable molecules. H2O (water) for example forms from two Hydrogen atoms and one Oxygen atom. Hydrogen atoms have 1 electron in their outer shell while oxygen has 6. So with 2 Hydrogen atoms and 1 Oxygen, you’ve got 8, which forms a stable molecule.
Nitrogen has 5 outer electrons, so when a Nitrogen gas molecule forms, they share 3 electrons to reach 8.
Argon, (and the other noble gasses) already has 8 electrons in its outer shells. This makes it very hard for it to form bonds. Noble Gases are naturally very stable and don’t react much with other elements. Argon doesn’t need to be bonded to another element to be stable, it can do that all on its own.
Argon and other atoms in the rightmost column of the periodic table are “noble” gasses. They are called this because they do not react with other atoms the vast majority of the time. So they stay as a singular atom.
To break it down further one way we model atoms is with electron “shells” essentially these are areas around the core nucleus of the atom that hold electrons. Each shell can only hold so many electrons before a new shell starts to be filled. An atom is most stable when its outer shell is filled. So nitrogen has an outer shell containing 5 electrons which is 3 short of a full outer shell. So another nitrogen molecule comes along missing 3 electrons, they grab on to 3 from each other forming a strong bond and now both atoms are stable. Oxygen does something similar with 2 missing electrons.
Now this is just a model, it describes behavior but not what is actually happening physically. What is actually happening is beyond my knowledge to describe.
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.
It’s because atom is not the unit of a material, you maybe have a misconception of what an atom is.
It’s a bit difficult to grasp, but the atom is a unit of the element itself. Like, one nitrogen atom is the smallest unit of nitrogen you can imagine. The problem is that most atoms don’t like to exist alone. Just because you can imagine a single atom of nitrogen, it doesn’t mean that it is stable in real world conditions.
So what atoms actually do if they find themselves in single -atomic state (which can happen for a short time), is that they stick together with other available atoms to form molecules. A molecule is basically several atoms stuck together. It may be two or more identical atoms (like two nitrogens) but may as well be different atoms such as nitrogen and oxygen to form various nitrogen oxides.
So these molecules are the units of actual material. Unlike atoms, molecules can stably exist.
Now how the atom exactly behaves when it somehow turns into single atomic stage, depends on the atom’s properties. Interestingly enough, there are some atoms that are actually stable in in a single atom state, and they are called noble gases. These are the only kind of atoms (not only argon but all of them), that are happy to not stick to other atoms, neither of the same kind, nor different.
Also it’s a weird terminology but noble gas atoms are often referred to as single atomic (or monoatomic) molecules which stretches the molecule definition a bit, but it gives you the general idea that the unit of real world material is not the atom but the molecule. If we look at argon atom as it’s also an argon molecule, then all of a sudden it’s clear that the base unit of the gas is a single molecule, not a single atom. Just the composition of the molecule is different.
Electrons are tiny magnets, and depending on how many an atom has it can be unstable and stick to other atoms.
Nitrogen atoms are unstable by themselves but stable in pairs of two, while Argon atoms are stable on their own due to the configuration of its electrons.
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