Does 11.2 dm3 of nitrogen consist of 0.5 moles at STP? Which of the following statements is true?
$\pu{11.2 dm^3}$ of nitrogen at STP-
A: has a mass of $\pu{14 g}$.
B: consists of $\pu{0.5 mol}$ atoms.

My instinct was that the answer is B because any gas has a volume of $22.4$ liters regardless of what the gas is. If $\pu{0.5 mol}$ of nitrogen has a volume of $\pu{11.2 dm^3}$ at STP, then $\pu{1 mol}$ of nitrogen has a volume of $22.4$ liters at STP (if I am correct).
It turned out the answer was A. Why is B not the correct answer?
You are right that 0.5 mol of $\ce{N2}$ is 11.2 L, but read the question carefully. Option B says that 11.2 L of $\ce{N2}$ contains 0.5 mol of atoms, which is wrong, it contains 11.2 L of $\ce{N2}$ contains 0.5 mol of molecules. It seems to be a trick answer. The first option is correct as 0.5 mol of $\ce{N2}$ has a mass of 14 grams.