Question

which have different numbers of electrons?
different ions of an element
different isotopes of an element
the nucleus of an element
each of the atoms of an element

Explanation:

1. Analyze "different ions of an element": Ions are formed by gaining or losing electrons. So different ions (e.g., \( \text{Na}^+ \) and \( \text{Na}^{2+} \) or \( \text{Cl}^- \) and \( \text{Cl}^{2-} \)) of the same element will have different numbers of electrons.
2. Analyze "different isotopes of an element": Isotopes differ in the number of neutrons, but have the same number of protons and electrons (in neutral state).
3. Analyze "the nucleus of an element": The nucleus contains protons and neutrons, no electrons. So nuclei don't have electrons to differ in number.
4. Analyze "each of the atoms of an element": Atoms of the same element (in neutral state) have the same number of electrons (equal to the atomic number).

So the correct option is the one about different ions of an element.

Answer:

A. different ions of an element