An isotope of the element Manganese (Mn) has an atomic number of 25 and a mass number of 55. Assuming the atom is neutral, this means it has
A) 55 protons, 55 electrons, and 25 neutrons
B) 25 protons, 25 electrons, and 30 neutrons
C) 25 protons, 30 electrons, and 25 neutrons
D) 25 protons, 25 electrons, and 55 neutrons

Question

Quizplus · Accepted Answer

The atomic number (25 for manganese) indicates the number of protons and, in a neutral atom, also the number of electrons. The mass number (55) is the sum of protons and neutrons. Therefore, with 25 protons, the number of neutrons is 55 - 25 = 30.

An Isotope of the Element Manganese (Mn) Has an Atomic