### Correct Option: C. 14 #### Detailed Explanation: 1. **Understanding Atomic Weight**: - Atomic weight (or atomic mass) is a measure of the mass of an atom, typically expressed in atomic mass units (amu). It reflects the average mass of an element's isotopes, weighted by their natural abundance. 2. **Isotopes of Nitrogen**: - Nitrogen has two stable isotopes: Nitrogen-14 (¹⁴N) and Nitrogen-15 (¹⁵N). - The most abundant isotope is Nitrogen-14, which has 7 protons and 7 neutrons, giving it an atomic mass of approximately 14 amu. - Nitrogen-15, which has 7 protons and 8 neutrons, is less abundant and has an atomic mass of about 15 amu. 3. **Calculating Average Atomic Weight**: - The atomic weight of nitrogen is calculated based on the relative abundances of its isotopes. The average atomic weight is approximately: \[ \text{Atomic Weight} = \left( \text{Fraction of } ¹⁴N \times 14 \, \text{amu} \right) + \left( \text{Fraction of } ¹⁵N \times 15 \, \text{amu} \right) \] - Given that about 99.6% of nitrogen in nature is ¹⁴N and about 0.4% is ¹⁵N, the calculation would yield an atomic weight very close to 14 amu. 4. **Why Option C is Correct**: - The atomic weight of nitrogen is commonly accepted as 14.01 amu, which rounds to 14. This value is widely used in chemistry and is found on the periodic table. #### Why Other Options are Incorrect: - **Option A: 10** - This value does not correspond to any known isotope of nitrogen. The lightest stable isotope, ¹⁴N, is significantly heavier than 10 amu. Thus, this option is incorrect. - **Option B: 12** - While 12 amu is the atomic weight of carbon (specifically the isotope ¹²C), it does not apply to nitrogen. Nitrogen's atomic weight is higher due to its isotopic composition. Therefore, this option is also incorrect. - **Option D: 16** - This value is closer to the atomic weight of oxygen (specifically the isotope ¹⁶O). Nitrogen does not have an atomic weight of 16 amu, making this option incorrect as well. ### Summary: - The atomic weight of nitrogen is approximately 14 amu, primarily due to the abundance of its isotope ¹⁴N. - Nitrogen has two stable isotopes: ¹⁴N and ¹⁵N, with ¹⁴N being the most prevalent. - The atomic weight is calculated based on the weighted average of these isotopes. - Options A (10), B (12), and D (16) do not correspond to nitrogen's atomic weight and are therefore incorrect. ### Revision Summary: - Atomic weight of nitrogen is approximately 14 amu. - Most abundant isotope of nitrogen is ¹⁴N. - Atomic weight reflects the average of isotopes based on their natural abundance. - Incorrect options do not correspond to nitrogen's isotopes or atomic weight.