Final answer:
To build an ionized model of an atom, you add or remove electrons, while to make a model that is radioactive, you change the number of protons, altering the element itself.
Step-by-step explanation:
The correct option : d
To ionize an atom, one would add or remove electrons, which alters the electrical charge of the atom without changing its atomic number. An atom becomes an ion when the number of electrons is not equal to the number of protons, resulting in a net charge. For instance, removing an electron from a neutral lithium atom, which normally has three electrons, would result in a lithium ion (Li+) with a +1 charge. To make an atom radioactive, one would alter the number of neutrons, protons, or both in the nucleus.
Changing the number of protons alters the element itself, such as transmuting one element into another in a nuclear reaction. Radioactive isotopes, also known as radioisotopes, have unstable nuclei and typically decay over time, emitting radiation. An ion is therefore an atom or molecule with a net electrical charge due to the loss or gain of one or more electrons. Radioactivity is a property of an atom that is dependent on the stability of its nucleus, which can be affected by changes in the number of protons or neutrons.