Number of atoms in the following samples of substances is largest in:

To determine which sample has the largest number of atoms, we need to compare the total number of atoms in each given sample. The number of atoms depends on the number of moles of the substance and the atomicity (number of atoms per molecule). The formula for the total number of atoms is:

Total atoms = (given mass / molar mass) × Avogadro's number × atomicity

Since Avogadro's number is constant, we can compare the values of (given mass / molar mass) × atomicity for each option. Let's calculate this for each substance.

Starting with option A: 4.0 g of hydrogen. Hydrogen is diatomic (H₂), so its molar mass is 2 g/mol and atomicity is 2. The calculation is:

Number of moles = given mass / molar mass = 4.0 g / 2 g/mol = 2.0 mol

Then, (given mass / molar mass) × atomicity = 2.0 × 2 = 4

Next, option B: 71.0 g of chlorine. Chlorine is diatomic (Cl₂), with molar mass = 2 × 35.5 = 71 g/mol and atomicity 2. The calculation is:

Number of moles = 71.0 g / 71 g/mol = 1.0 mol

Then, (given mass / molar mass) × atomicity = 1.0 × 2 = 2

Option C: 127.0 g of iodine. Iodine is diatomic (I₂), with molar mass = 2 × 127 = 254 g/mol and atomicity 2. The calculation is:

Number of moles = 127.0 g / 254 g/mol = 127/254 = 0.5 mol

Then, (given mass / molar mass) × atomicity = 0.5 × 2 = 1

Option D: 48.0 g of magnesium. Magnesium is monatomic (Mg), with molar mass = 24 g/mol and atomicity 1. The calculation is:

Number of moles = 48.0 g / 24 g/mol = 2.0 mol

Then, (given mass / molar mass) × atomicity = 2.0 × 1 = 2

Comparing the values:

• Option A: 4
• Option B: 2
• Option C: 1
• Option D: 2

The largest value is 4, from option A (4.0 g of hydrogen). Therefore, the sample with the largest number of atoms is 4.0 g of hydrogen.

Hence, the correct answer is Option A.