The atomic mass of nitrogen is approximately 14.01 atomic mass units (amu). This is the weighted average of the masses of all the naturally occurring isotopes of nitrogen.
Here's a breakdown of how this value is determined:
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Understanding Atomic Mass: Atomic mass is the mass of an atom, typically expressed in atomic mass units (amu) or Daltons (Da).
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Nitrogen Isotopes: Nitrogen primarily exists as two isotopes:
- Nitrogen-14 (14N): Contains 7 protons and 7 neutrons. It's the most abundant isotope.
- Nitrogen-15 (15N): Contains 7 protons and 8 neutrons. It's a much less abundant isotope.
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Isotopic Abundance: The key is to know the abundance of each isotope in a natural sample of nitrogen. Typically:
- 14N accounts for approximately 99.636% of naturally occurring nitrogen.
- 15N accounts for approximately 0.364% of naturally occurring nitrogen.
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Calculation: The atomic mass is calculated as a weighted average of the masses of the isotopes. Assuming the mass of 14N is approximately 14 amu and the mass of 15N is approximately 15 amu, the calculation is:
Atomic Mass = (Abundance of 14N Mass of 14N) + (Abundance of 15N Mass of 15N)
Atomic Mass = (0.99636 14 amu) + (0.00364 15 amu)
Atomic Mass ≈ 13.949 + 0.055
Atomic Mass ≈ 14.004 amu
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Therefore, the atomic mass of nitrogen is approximately 14.01 amu. This value is usually found on the periodic table.
Important Note: The molar mass of nitrogen, which is the mass of one mole of nitrogen atoms, is approximately 14.01 grams/mole. This value is numerically the same as the atomic mass but has different units.
