With Version 10 of Mathematica/Wolfram, there are now two ways to make curated data calls:
ElementData[#,"AtomicMass"]&/@Range[88]
and
ElementData[#]["AtomicMass"]&/@Range[88];
The difference between the two is subtle; the first (traditional) method returns answers with Head = Quantity (or some Number format in versions < 10) and the second form returns answers with Head = Entity. Entities are apparently new and possibly useful; however I noticed that the first call requires 0 cloud credits while the second requires 176 Cloud Credits.
Is there a reason why I should pay for the data as opposed to get it for free? Is the Entity Head worth racing through 37% of my credit allocation in one function call?
Heaven forbid if I had wanted atomic radii and ionization energies along with their masses.