According to google, one gallon equals 8.36 pounds. I took 8.36and divided by 0.00590 and got 1416.94915254 So if rounded to the nearest hundreth, 1416.95. I have no idea if I'm right. Sorry I couldn't do more!
The atomic number is the number of protons in the nucleus of an atom. The number of protons define the identity of an element (i.e., an element with 6 protons is a carbon atom, no matter how many neutrons may be present).