What value correctly represents Avogadro's number?

• A. 6.022 × 10^24
• B. 1.602 × 10^-19
• C. 3.00 × 10^8
• D. 6.022 × 10^23

Answer: (D)

Avogadro's number is the number of particles in one mole of a substance, which lets us connect the microscopic world of atoms and molecules to macroscopic amounts we measure in grams. It tells us that one mole contains about 6.022×10^23 particles, whether we’re counting atoms, ions, or molecules depending on the substance. This is why 12 g of carbon-12 contains exactly 6.022×10^23 carbon atoms. The other numbers refer to different ideas: 6.022×10^24 would be ten times as many particles per mole, 1.602×10^-19 is the elementary charge, and 3.00×10^8 is the speed of light. So the value that correctly represents Avogadro's number is 6.022×10^23.