Answer
🔬 Atomic Structure: Carbon-13 (¹³C)
Question:
An atom of ¹³C contains ________ protons.
✅ Correct Answer: 6
All carbon atoms, regardless of isotope, have 6 protons. The number of protons is what defines the element.
🧠 Explanation
The notation ¹³C represents an isotope of carbon with:
- Mass number (A) = 13
- Atomic number (Z) = 6 → This tells us the number of protons
- Neutrons = 13 − 6 = 7
Mass number = Protons + Neutrons
🔍 Why Other Options Are Incorrect
| Option | Why It’s Incorrect |
|---|---|
| 7 | Number of neutrons in ¹³C, not protons |
| 9 | Would correspond to fluorine (atomic number 9) |
| 13 | This is the mass number (protons + neutrons), not the proton count |
| 19 | Unrelated to carbon; does not match any atomic property of ¹³C |
🧾 Summary
- Atomic number (Z) determines the number of protons.
- Carbon (C) always has 6 protons.
- ¹³C is an isotope with 7 neutrons and 6 protons.
✔ Final Answer: 6 protons