Which of the following has the greatest mass? 1 mole of uranium (U) 1 mole of oxygen (O) 1 mole of sodium (Na) 1 mole of chlorine (Cl)

To determine which has the greatest mass, we need to find out the molecular mass of each element:

Uranium (U) = 238 g/mol

Oxygen (O) = 16 g/mol

Sodium (Na) = 23 g/mol

Chlorine (Cl) = 35.45 g/mol

Therefore, if we have one mole of each element, the element with the greatest mass is 238 grams or Uranium.