Which of the following samples contains the greatest number of atoms?

• A. 23.0 g of Na
• B. 18.0 g of H2O
• C. 4.0 g of He
• D. 12.0 g of C

Answer: (C)

Verified step by step guidance

1. Identify the molar mass of each substance using the periodic table: sodium (Na), water (H\_2O), helium (He), and carbon (C).
2. Calculate the number of moles for each sample using the formula: \(\text{moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}}\).
3. Determine the number of atoms in each sample. For elemental substances (Na, He, C), the number of atoms equals the number of moles times Avogadro's number (\$6.022 \times 10^{23}$ atoms/mol). For water (H\_2O), multiply the number of moles by Avogadro's number and then by 3 (since each molecule contains 3 atoms: 2 H and 1 O).
4. Compare the total number of atoms calculated for each sample to identify which one contains the greatest number of atoms.
5. Conclude by selecting the sample with the highest total atom count based on your calculations.