Identify the part of the atom that most determines the chemical properties of the atom.

Question

The number of shells

The number of electrons

The number of neutrons

The number of protons

Answer 1

Let's look at it this  way.  If we change the number of  electrons we just change the charge of the element; in other words we get an ion, but it's still the same element only with a different charge.  If we change the number of neutrons we get an isotope and  change the atomic mass, but it's still the same element with same number of protons as the original, only different number of neutrons, different atomic weights, but different forms of the same element.  Now, adding or removing a proton is a whole different animal.  It changes the charge of the nucleus and the atomic number.  As we know  the atomic number is  the number of  protons in the nucleus, so if we add or take away a proton we get a completely different element.  For example, let's add a proton to hydrogen changing the atomic number from 1 to 2.  Now we have helium and completely different element.  Shells are just the orbital levels and patterns the electrons occupy when buzzing around the nucleus.

Answer 2

The number of protons in the nucleus determines which element it is.  However, the number of electrons in the outer shell, i.e. the number of valence electrons, determines the chemical reactions that the element can participate in.  But that does not appear in the list of choices.  If you have to select an answer from the given list, then select the number of protons, because if that is different, you will not even have the same element.  But keep in mind that the possible chemical reactions are determined by the outer shell electrons.