Question

adding a proton to the nucleus of an atom (or removing one), and an electron along with it, changes that atom into a new
options:
○ isomer ○ isotope. ○ molecule
○ ion. ○ element.

Explanation:

• Isomer: Same formula, different structure (not about proton change).
• Isotope: Same element, different neutrons (not protons).
• Molecule: Group of atoms (not about changing an atom's identity).
• Ion: Charged atom (due to electron gain/loss, not proton change).
• Element: Defined by proton number. Changing protons (and electron) changes the element.

Answer:

element