You have 10.0 g each of Na, Mg, and Al. Which sample contains the greatest number of atoms?

• A. Na
• B. Mg
• C. Al

Answer: (A)

Verified step by step guidance

1. Step 1: Identify the molar mass of each element. Use the periodic table to find the atomic masses: Sodium (Na) ≈ 22.99 g/mol, Magnesium (Mg) ≈ 24.31 g/mol, Aluminum (Al) ≈ 26.98 g/mol.
2. Step 2: Calculate the number of moles for each element using the formula: \(\text{moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}}\). For each element, divide 10.0 g by its molar mass.
3. Step 3: Recall that the number of atoms is proportional to the number of moles, since 1 mole contains Avogadro's number (\$6.022 \times 10^{23}$) of atoms.
4. Step 4: Compare the moles calculated for Na, Mg, and Al. The element with the greatest number of moles will have the greatest number of atoms.
5. Step 5: Conclude which element has the greatest number of atoms based on the highest mole value calculated.