## Chemistry (7th Edition)

$_{35}^{33}Br$ can't be correct.
The mass number (top left number) for the element is calculated by: Mass number = Number of protons + Number of neutrons. Since all numbers must be positive, the mass number must be greater than or equal to the number of protons. ** Number of protons = Z (Bottom left number) For $_{35}^{33}Br$ : $33 = 35$ + Number of neutrons. Number of neutrons = 33 - 35 = -2 It doesn't make sense to have "-2" neutrons in a nucleus.