What is the mass of 1.21 × 1021 atoms of sulfur? (NA = 6.022 × 1023 mol–1)

Divide the atoms of sulfur by avogadro's number (6.02 x 10^23 mol)

(1.21 x 10^21) / (6.02 x 10^23)

= 0.00200996678

Molar mass of Sulfur (listed in your periodic table) = 32.06g/mol

moles = mass/molar mass

mass = molar mass x moles

Mass of Sulfur = (32.06) x (0.00200996678) = 0.06g of Sulfur

if two electrons have the same n, the same ℓ, and the same ml, then they are in the same orbital. the pauli exclusion principle states that no two identical fermions (a fancy word for electrons and other subatomic particles like electrons) may occupy the same quantum state in an atom simultaneously.