How many moles are in 0.0073 kg of tantalum?

Tantalum is the 73rd element in the periodic table with an atomic mass equal to 180.95 g/mol. To determine the number of moles present in the given mass of tantalum above, we simply divide the mass by the atomic mass. 
                   number of moles = (0.0073 kg)(1000 g/ 1kg) ÷ (180.95 g/mol)
                   number of moles = 0.0403 moles
Therefore, there is approximately 0.0403 moles of tantalum in 0.0073 kg.