Eli5: what are things like carbon-12? Are they carbons but with a nucleon mass of 12? And how are electrons related?
In: Chemistry
All carbon atoms have the same number of protons, the positively charged particle in the nucleus of the atom. This is true for every element – the number of protons is what determines what element it is. Carbon atoms always have 6 protons.
However, elements can have different numbers of neutrons, a particle with no charge. Adding up the number of protons and neutrons gives you the isotope number. Carbon-12 has 6 neutrons. Carbon can also exist as carbon-13 with 7 neutrons (relatively common, about 1 in 100 carbon atoms in the environment are 13C) and carbon-11 with 5 neutrons (11C is not stable and decays rapidly).
Isolated carbon atoms don’t exist in nature, but uncharged carbon atoms have one electron for each proton. Two of these are non-bonding and four of them participate in bonding with other elements.
Carbon is any atom with 6 protons. Carbon-12 is specifically atoms with 6 protons and 6 neutrons (for a total of 12 nucleons). It is the most common form of carbon naturally occurring (98.89% of natural carbon is carbon-12).
Electrons don’t factor into whether carbon is carbon-12. Electrons only care about the number of protons, not the number of neutrons. All carbon has 6 protons, so all carbon is carbon to an electron.
Isotopes have more or fewer neutrons than other atoms of it’s kind.
Electrons are not being considered when we talk about things like Carbon-12. Having more or fewer electrons causes an atom to be an ion (for example, sodium chloride dissociates into a pair of Na+ and a Cl- ions, one with an extra electron and one with a missing electron)
so back to isotopes; Carbon-12 and Carbon-14 have the same number of protons and electrons, with Carbon-14 having **two extra neutrons**. This makes it heavier but does not change the atomic number (same number of protons) or the electric charge (same number of electrons). Extra neutrons makes the atom heavier and typically less stable.
Cabon is an atom with 6 protons with a positive charge in the core and as a result, 6 electrons to get a neutralize the charge
The core also contains a neutron and they are natural charges so no extra electrons.
So carbon-12 has 12 particles in the nucleus. 6 of them are protons else it is not carbon so 6 are neutrons. This is the nucleon number
The number of neutrons vs protons determine how stable the nucleus is in a not straightforward way. To many or to few neutrons can result in an unstable nucleus For the element with many protons like Uranium, there can be no stable isotopes.
Carbon-12 has an atomic mass of 12 u(unified atomic mass unit) because that is what was used to define it. Carbon-14 has a mass of 14.003241 u. This is not just the nucleus but include the electrons too so the carbon-12 nucleus mass is slighty below 12
The exact mass of the atom is the mass of the protons and neutrons and the electrons made of minus the binding energy of the nucleus you can [look at it here](https://en.wikipedia.org/wiki/Nuclear_binding_energy#/media/File:Binding_energy_curve_-_common_isotopes.svg)
a proton has a mass of 1.007276466621 u and a neutron off 1.00866491588 u The electron mass is only 0.000548579909070 u so a proton and a neutron have a bit less mass than a neutron.
So atoms can have masses of slightly above or below the nucleon number.
For elements, you often find the average mass of the isotopes in the proposition that exist on earth. So carbon has a mass of 12.0107u as most are Carbon-12 but some are Carbon-14 and the given value the average mass
It’s exactly what you said, it’s a carbon atom with 12 nucleons. [element]-[mass #] is a common way to define isotopes of each element. For instance, carbon-14 would have 6 protons and 8 neutrons. Carbon will always have 6 protons (because that’s what makes it carbon) so additional/reduced atomic mass will always be from changing the number of neutrons.
Electrons aren’t dignified in this notation, it tells you nothing about the electric charge other than the number of protons. When you involve electrons, you’re talking about ions, not isotopes. Isotopes can be ionic but not always.
I think you are talking about isotopes.
Have a look at a periodic table. There are 2 numbers for every element. The smaller number is the atomic number, that’s the number of protons. This is what defines an element. Crbon always has 6 protons, if it had 7 it would be nitrogen.
The bigger number is the mass number, which is the number of protons and neutrons. Protons and neutrons have a similar mass(1 atomic mass unit), so this is also the mass of the atom. Electrons are ignored since they are significantly lighter and tend to get attracted to other atoms.
Carbon-12 has a mass number of 12. Since it’s carbon it has 6 protons, so it must have 6 neutrons. Carbon-13 has 6 protons and 7 neurons. Carbon-14 has 6 protons and 8 neutrons, but since it has so many neutrons it’s unstable and undergoes radioactive decay. Radioactive decay is where isotopes are most useful, since carbon-14 is radioactive but carbon-12 isn’t.
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