O-18, an isotope of oxygen, has a stable nucleus. o-19, another isotope of oxygen, does not have a stable nucleus. based on this information, which statement is correct?
-o-19 is radioactive; o-18 is not radioactive.
-o-19 has a mass defect; o-18 does not have a mass defect.
-o-19 has a nuclear binding energy; o-18 does not have a nuclear binding energy.
-o-19 has more neutrons than protons; o-18 has equal numbers of neutrons and protons.

first option, O-19 is radioactive; O-18 is not radioactive.

Explanation:

1) Radioactivity is the spontaneous emission of α (alpha) particles, β (beta) partilces, or γ (gamma) rays.

2) The above mentioned emissions come from the nucleus decay of isotopes.

3) The elements with unstable nuclei emitts radiaton spontaneously and are called radioactive.

4) Having been told that oxygen-18 has a stable nucleus, means that it does not emit radiation spontaneously, ergo it is not radioctive.

5) On the other hand, since oxygen-19 does not have a stable nucleus, it emitts ratiation spontaneoulsy and is called radioactive.

Oxygen-18 means that the mass number of this isotope is 18, and oxygen-19 means that this isotope has mass number 19. Mass number is the sum of the number of protons and neutrons.