Which of the following is the number of hydrogen atoms in a mole of hydrogen gas at STP?
a) 224
b) 6,02 x 1023
c) 1,20 x 1024
d) 2.016
e) 1.008

The mass of Cu-63 is 63 amu.

Chemical elements are represented using their symbols, their mass number and their proton numbers. The mass number of this isotope of copper is shown next to the symbol. Regardless of the mass of the isotopes, their proton number is the same, which is 29.