Comparing C4+ and C4- Ions: Charge Differences

[FeDeX_LaTeX]

Hello;

I was told today that you can get two different types of carbon ion, C⁴⁺ and C^4-. My question is, how are they any different? What is the difference between the two ions that causes the reverse of charge?

Thanks.

 

[Borek]

What's the difference? Number of electrons.

But reality is not that simple. I am more than sure that in correct conditions one can observe many more ions. And I am almost sure that neither C⁴⁺ nor C^4- will dominate, even if there are reasons why they could be relatively more stable.

 

[mikelepore]

To form a positive ion, the consideration is the ionization energy, the amount of energy that must be added to a neutral atom to remove an electron.

To make a negative ion, the consideration is the electron affinity, the amount of energy that gets released when an electron is accepted.

These values are given in tables for all elements. By looking them up and comparing them, a person can figure out whether a given element is more likely to form a positive ion or a negative ion.

I'm not too experienced in actually doing this, but that's the general idea.

 

[mikelepore]

If the atomic number is 6, then the electron configuration is 1s2 2s2 2p2. The maximum number of electrons allowed in each of the sublevels 1s, 2s and 2p are 2, 2, and 6, but the number of electrons in them is 2, 2, and 2, assuming neutral carbon. The C +4 ion means it has lost the four electrons that were in the 2s and 2p sublevels, leaving a final configuration of 1s2. The C -4 ion means that the added four electrons have filled up the 2p sublevel, leaving a final configuration of 1s2 2s2 2p6. Both of these ions have their outermost energy level filled, so both of them are stable.

 

[Borek]

Both of these ions have their outermost energy level filled, so both of them are stable.

This argument works OK for ions of lower charge, the higher the charge gets, the less stable ions are. That's why I wrote earlier that there are reasons that they could be more stable, but I don't think it will be easily to observe.

I am known to be occasionally wrong, this can be one of these cases.