using the periodic table, elaborate the difference between the number of electrons in an oxygen-16 atom and…

Brief Explanations:

To determine the correct answer, we analyze each option:

• Option A: Oxygen atoms have an atomic number of 8, so the number of electrons in a neutral oxygen atom is 8. Different electron numbers would imply different elements (e.g., 9 electrons would be fluorine), so A is incorrect.
• Option B: Allotropes are different forms of the same element (e.g., O₂ and O₃), not different isotopes. Isotopes differ in neutron number, not electron number. Oxygen - 16 and oxygen - 18 are isotopes, not allotropes, and they have the same number of electrons (8), so B is incorrect.
• Option C: The number of electrons in a neutral atom is equal to the atomic number. Oxygen has an atomic number of 8, so both oxygen - 16 and oxygen - 18 (which are isotopes, differing in neutron number) have 8 electrons. The statement about oxygen atoms fluctuating in electron number is wrong, so C is incorrect.
• Option D: Isotopes of an element have the same atomic number (and thus the same number of electrons) but different mass numbers (due to different neutron numbers). Oxygen - 16 and oxygen - 18 are isotopes of oxygen, so they both have 8 electrons (since oxygen's atomic number is 8). This statement is correct.

Answer:

D. The number of electrons are the same for all isotopes of an element - so both oxygen - 16 and oxygen - 18 contain 8 electrons.