Hi,

I'm a wee bit confused here.

An isotope is an atom (or is it a molecule?) that has the same number of electrons as another atom/molecule of the same element but has a different number of nucleons, right?

For example, Cl 35 and Cl 37 are isotopes just like C 12 and C 14.

However, could someone please explain what an ion is because I can't figure it out.


Thanks,

-Xm8

You're about right on the isotope, the number of protons affects the element, an atom with 6 protons is always carbon, what changes is the number of neutrons (and therefore the total number of nucleons - but it's always the neutrons that change). This also means that neutral atoms also always have the same number of electrons - because the electrons just balance the charge of the protons. I believe that the term isotope refers to the atoms - you can get molecules with isotopes in them, for example heavy water is D2O instead of H2O, where D is deuterium, an isotope of hydrogen with a proton and a neutron.

Your examples are perfect. Some people say that carbon-14 is an isotope of carbon-12, because c12 is more prevalent, however it's more correct to say that both c12 and c14 are isotopes of "carbon" (the element with 6 protons).

an ion is simple compared to an isotope. It's simply an atom with unbalanced charge, i.e. a different number of electrons that protons. These are denoted with a + or -, for example Fe^{2+} has 2 less electrons than protons, Cl^- has 1 more electron than protons. These are normally formed by the addition or removal of electrons from the stable atom (i.e. ionisation).

Hope this helps and if you have more questions please feel free to ask.

Hello Capuchin,

Thanks for your answer. I understood everything although there are still a few things I'm not sure about.


but it's always the neutrons that change

Do you mean that when you have an isotope, the atom's electrical charge is still neutral because the number of protons is equal to that of the electrons. However, it is the number of neutrons that change, thus effecting the total number of nucleons (protons + neutrons). Am I right in saying this?

Moreover, I understand the concept of ions now, however what makes these molecules become electrically unbalanced?

And by the way, which atoms (specifically) try to grab a second or eighth electron on their outershell? It's not only ions, right?


Thanks a lot,

-Xm8

Hello Capuchin,

Thanks for your answer. I understood everything although there are still a few things I'm not sure about.

Do you mean that when you have an isotope, the atom's electrical charge is still neutral because the number of protons is equal to that of the electrons. However, it is the number of neutrons that change, thus effecting the total number of nucleons (protons + neutrons). Am I right in saying this?

You can have ionised isotopes too.


Moreover, I understand the concept of ions now, however what makes these molecules become electrically unbalanced?

Generally some kind of process, for example firing an electron beam at a small amount of sample can ionise it positively, as electrons are knocked out of the orbitals.


And by the way, which atoms (specifically) try to grab a second or eigth electron on their outershell? It's not only ions, right?

Are you thinking of compounds? Atoms prefer to have full outer rings, and so will more readily react with substances which can provide that. This isn't really linked to ions.

Thanks for your answers, very helpful indeed :)

I was just wondering, do you know what an "electronic cloud" means? Is it an atom's outer shell?

Now you're getting a bit more deep into the physics. You've learnt that electrons orbit around the nucleus in neat orbits, but this is only really a useful model, and not really like reality. In reality, the electrons are jitting around from state to state, and so they all form a "cloud" around the nucleus.

Hope this helps a little.

Thanks again Capuchin,

Most helpful once again.