[Leeroy]

Hello,

I am fairly new to chemistry and am still learning the basic concepts within the world of chemistry. I have a question related to chemical elements and is as follows:

I understand that there are around 117 chemical elements. Every element is composed of atoms, and every atom is composed of subatomic particles (protons, neutrons and electrons). I know that you can delve further into the study and particle physics, but I just want to talk about the basics.

Take oxygen, a fundamental Element. A molecule of oxygen contains 2 atoms that are bonded covalently. So when we say oxygen as an element, rather than a molecule, am I right in assuming that we're not mean to quantify an element in the strictist sense? I.e. One element of oxygen contains xxx number of atoms.

I'm confused about this because it says that all elements are composed of atoms, but how many atoms? I have seen many definitions for Elements and am still confused. On the periodic table, O for oxygen, does this mean that the one O for oxygen only contains one atom? Because it seems that an atom is pretty much the same definition as an element in certain cases.

This is how I see it, please correct me if I am wrong: An atom is the smallest unit of an element that possesses all the characteristics of that element. An element is a substance that cannot be broken down any further. All elements are made up of certain atoms, and each atom of that particular element is identical. For instance, atoms of oxygen are different from the atoms of gold etc.

So, if you're confused about the question that I've asked, I just want to know how many atoms are in elements in their periodic table state (if you know what I mean)? Is it one atom per element? Because Oxygen (O2) the molecule has 2 atoms, therefore I must assume that O on its own is just one atom?

Am I getting concepts confused?

Thanks for your time.

[Mitch]

The properties listed on the periodic table are assuming one atom elements. Since the oxygen that we breathe is diatomic we tend to use that noun to refer to diatomic oxygen as well. It is up to the speaker to clearly state which form is being discussed, although it will be typically the diatomic form.

[ifuller]

You will also notice that the oxygen located on the periodic table has a atomic mass of 15.999. However, the oxygen we breath has a mass of approximately 32, or two of the oxygen atoms located on the table. There are several isotopes of atoms that can exist in nature. For example you can also have O3 which is also known as Ozone. However, the isotope that we hear about most is the most abundant one in the environment. Hope this helped.

[Leeroy]

Thank you very much for the replies.

Can an atom exist that is not an atom of an element? I know that an atom is defined as the smallest unit of an element, showing all of the characteristics of that element - but can an atom exist that is not related to any of the 117 elements, like an orphen atom as it were?

[Mitch]

Closest thing would be a neutron, which has no protons.

[Mitch]

Positronium would also be the closest thing to an element I can think of: http://en.wikipedia.org/wiki/Positronium

[Leeroy]

Thanks for the link, I'll take a read.

It's very interesting to me, why do you think that it's called 'the periodic table of elements' rather than 'the periodic table of atoms'? Because at the end of the day, elements are just different types of atoms... Is it so that people do not confuse concepts?

[Mitch]

I think it sounds better as elements.