Avogadro's number is defined as...

• A. 6.022×10^23 particles per mole; it links moles to the number of particles by multiplying moles by NA to obtain particles.
• B. 6.022×10^23 moles per particle; it converts particles to moles.
• C. 6.022×10^23 volume units per mole; relates moles to volume.
• D. 6.022×10^23 seconds per mole; relates time to amount.

Answer: (A)

Avogadro's number is the bridge between the amount of substance in moles and the actual count of individual particles. It tells us that one mole contains 6.022×10^23 particles, so you convert moles to particles by multiplying by this number. For example, 0.50 mole of a substance contains about 0.50 × 6.022×10^23 ≈ 3.01×10^23 particles. This constant is not a measure of volume or time, nor is it the reciprocal of moles per particle; it is specifically particles per mole, which is why multiplying moles by NA yields the number of particles.