1. Find the Molar Mass of Ca(NO₃)₂

* Calcium (Ca): 40.08 g/mol

* Nitrogen (N): 14.01 g/mol (multiplied by 2 because there are two nitrogen atoms)

* Oxygen (O): 16.00 g/mol (multiplied by 6 because there are six oxygen atoms)

Total molar mass = 40.08 + (14.01 * 2) + (16.00 * 6) = 164.10 g/mol

2. Calculate the Moles of Ca(NO₃)₂

* Moles = mass / molar mass

* Moles = 7.5 g / 164.10 g/mol ≈ 0.0457 mol

3. Calculate the Number of Nitrogen Atoms

* Each mole of Ca(NO₃)₂ contains 2 moles of nitrogen atoms.

* Total moles of nitrogen atoms = 0.0457 mol * 2 = 0.0914 mol

* To convert moles to number of atoms, use Avogadro's number (6.022 x 10²³ atoms/mol):

* Number of nitrogen atoms = 0.0914 mol * 6.022 x 10²³ atoms/mol ≈ 5.50 x 10²² atoms

Therefore, there are approximately 5.50 x 10²² nitrogen atoms in 7.5 g of Ca(NO₃)₂.