What's the maximum amount of electrons that will fit on an outermost shell of an atom?
a. 10
b. 12
c. 8
d. 4

5 an atom may have any number of electron shells, theoretically that is! typically, the number of electrons that you can fit on the first few electron shells are 2 on the 1st, 8 on the 2nd, 18 on the 3rd, 18 (or sometimes 32) on the 4th, usually 32 for the 5th shell... and so on... it gets complicated and there are various rules for computing the number of electrons on each shell depending on if it a gas, metal, or many other things. so, in general, the number of electron shells that an atom can have depends on the number of electrons in the atom! so the more electrons you put on an atom (whether you are making an ion, or going to bigger elements), the more electron shells it is going to have! however, you couldn't really put an infinite number of electron shells on an atom (given that you have an infinite amount of electrons). this is because the atom gets very unstable as is gets bigger. uranium-235, for example, (which has 7 electron shells, and the corresponding number of electrons and protons) is much too unstable because its nucleus has too many protons and it wants to decay into 2 smaller atoms. so, in uranium-235's case, there are simply too many protons - and the same number of electrons, and hence a lagre number of electron shells - to be stable and remain one atom. so, there is a limit to how many shells you can have, but it would depend on the stability of the atom. although, i suppose you could theoretically create an atom (in a lab) with an obscenely high number of electrons for a fraction of a second before it decayed. so in short, there is no theoretical limit, but there is a practical, dependant limit. if i had to guess as to what this real limit is for the atoms which we know, i would say it is about 7, maybe 8, but i very much doubt it.