How to Calculate Atoms?

To calculate the number of atoms in a sample of a substance, you generally use the following formula:

Number of atoms = Number of moles × Avogadro's number

Here's a breakdown of the process:

1. Determine the Number of Moles:

• If you are given the mass of the substance, you need to convert it to moles. To do this, use the following formula:

  Number of moles = Mass (g) / Molar mass (g/mol)

  • The molar mass is found on the periodic table. For example, the molar mass of Tin (Sn) is approximately 118.71 g/mol.

2. Use Avogadro's Number:

• Avogadro's number is a fundamental constant that represents the number of atoms, molecules, or ions in one mole of a substance. It is approximately 6.022 x 10²³ particles/mol.

3. Apply the Formula:

• Once you have the number of moles, multiply it by Avogadro's number to find the number of atoms.

Example:

Let's calculate the number of atoms in 2g of Tin (Sn).

1. Calculate the number of moles of Sn:

   Number of moles = 2 g / 118.71 g/mol ≈ 0.01685 mol

2. Calculate the number of atoms of Sn:

   Number of atoms = 0.01685 mol × 6.022 × 10²³ atoms/mol ≈ 1.015 × 10²² atoms

Therefore, there are approximately 1.015 × 10²² atoms in 2g of Tin.

In summary, calculating the number of atoms involves converting a given mass into moles and then multiplying by Avogadro's number to determine the total count of individual atoms present.