The atomic weight of nitrogen is?

Analysis

The question asks for the standard atomic weight (or relative atomic mass) of the element Nitrogen. In chemistry, this value represents the average mass of an atom of an element compared to one-twelfth of the mass of a carbon-12 atom.

Concept

The periodic table organizes elements based on their atomic number (number of protons). Nitrogen is the 7th element in the periodic table. Its most abundant isotope is Nitrogen-14, which consists of 7 protons and 7 neutrons. While there are trace amounts of other isotopes (like Nitrogen-15), the weighted average mass used in standard chemical calculations is approximately 14.007, which is rounded to 14 for most secondary school examinations.

Solution

1. Identify the element: Nitrogen (Symbol: N).
2. Locate in the Periodic Table: Nitrogen is in Group 5, Period 2, with an atomic number of 7.
3. Determine the mass number: The mass number is the sum of protons and neutrons. For the most common isotope of Nitrogen, $7 \text{ protons} + 7 \text{ neutrons} = 14$.
4. Compare with options: • A: 10 (Incorrect) • B: 12 (This is the atomic weight of Carbon) • C: 14 (Correct) • D: 16 (This is the atomic weight of Oxygen)

Exam Tip

To remember atomic weights for common elements, use the "Even Atomic Number Rule" for light elements: for many elements with an even atomic number (like Carbon-6, Oxygen-8, Neon-10), the atomic weight is roughly double the atomic number. Nitrogen is an exception to this rule because it has an odd atomic number (7), but its mass is 14. Just remember: Nitrogen is 7, so double it to get 14!