To know the right answer,. let us define each of the following choices.
1. Isotope is a group of atoms that belong to same element but differ on their mass numbers. As written in the periodic table, each element has a specific value of atomic numbers which represent the number of protons in the atom. But they may differ when it comes to the number of neutrons in the nucleus.
2. Compound is a combination of at least two elements together that are bonded by intermolecular forces like ionic or covalent bonding, electrostatic forces and London dispersion forces.
3. Water is a compound made up of two hydrogen atoms and one oxygen atom.
4. Ions are atoms of elements that are not neutral because they readily accep ot gain electrons from other elements. So, they exist as cations (positively charge ions) or anions (negatively charge ions).
Basing on the descriptions of each choice, the answer to the description of atoms with an electrical charge is an ion.
