History: A nucleus of **hydrogen** always has one proton (Z = 1), and in nature, 99.98% of all hydrogen nuclei have 0 neutrons (N = 0). What is the mass number A?

A nucleus of hydrogen always has one proton (Z = 1), and in nature, 99.98% of all hydrogen nuclei have 0 neutrons (N = 0). What is the mass number A?

• 2
  A = N+Z = 0+1 = 1
• 0
  A = N+Z = 0+1 = 1
• 1
  Correct!
• -1
  A = N+Z = 0+1 = 1