Question

carbon-13 and carbon-14 are isotopes of carbon. which of the statements is/are true?
i. carbon-12 is also an isotope of carbon.
ii. these isotopes have the same number of electrons.
iii. these isotopes have the same number of protons.
iv. these isotopes have the same number of neutrons.

○ ii, iii

○ i, ii, iii, iv

○ iii only

○ i, ii, iii

Explanation:

1. Statement I: Isotopes of an element have the same atomic number (number of protons) but different mass numbers (sum of protons and neutrons). Carbon - 12, Carbon - 13, and Carbon - 14 all have atomic number 6 (so they are isotopes of carbon), so I is true.
2. Statement II: In a neutral atom, the number of electrons is equal to the number of protons. Since isotopes of carbon have the same number of protons (atomic number 6), they will have the same number of electrons (assuming they are neutral), so II is true.
3. Statement III: By definition, isotopes of an element have the same number of protons (same atomic number), so III is true.
4. Statement IV: The number of neutrons = mass number - atomic number. For Carbon - 13: neutrons = 13 - 6 = 7; for Carbon - 14: neutrons = 14 - 6 = 8; for Carbon - 12: neutrons = 12 - 6 = 6. So the number of neutrons is different for these isotopes, so IV is false.

So statements I, II, and III are true.

Answer:

I, II, III