Question

Which among the following elements has the highest number of atoms in 1 g each?
(at. no. Au = 197, Na = 23, Cu = 63.5, Fe = 56)

• A. Cu(s)
• B. Na(s)
• C. Au(s)
• D. Fe(s)

Hint:

The element with the lowest atomic mass will have the highest number of atoms in 1 gram.

Answer 1

The Correct Option is B

Step 1: Understanding Avogadro’s number and molar mass.
The number of atoms in 1 g of a substance is given by the formula: \[ \text{Number of atoms} = \frac{1}{\text{molar mass}} \times \text{Avogadro’s number} \] The substance with the smallest molar mass will have the highest number of atoms in 1 g.
Step 2: Calculation.
- For Na: \(\frac{1}{23} \times 6.022 \times 10^{23} = 2.61 \times 10^{22}\) atoms. - For Cu: \(\frac{1}{63.5} \times 6.022 \times 10^{23} = 9.47 \times 10^{21}\) atoms. - For Au: \(\frac{1}{197} \times 6.022 \times 10^{23} = 3.06 \times 10^{21}\) atoms. - For Fe: \(\frac{1}{56} \times 6.022 \times 10^{23} = 1.08 \times 10^{22}\) atoms.

Step 3: Conclusion.
Sodium (Na) has the highest number of atoms in 1 g. The correct answer is (B) Na(s).