An atom of the element iron has an atomic number of 26 and an atomic mass number of 56. If it is neutral, how many protons, neutrons, and electrons does it have?
A)26 protons, 30 neutrons, 30 electrons
B)26 protons, 30 neutrons, 26 electrons
C)13 protons, 56 neutrons, 13 electrons
D)13 protons, 43 neutrons, 13 electrons
E)26 protons, 56 neutrons, 26 electrons

Question

Quizplus · Accepted Answer

The atomic number (26) tells us the number of protons, which in a neutral atom is equal to the number of electrons. So, it has 26 protons and 26 electrons. The atomic mass number (56) is the sum of the number of protons and neutrons. Therefore, the number of neutrons is 56-26=30. Choice A is incorrect because it has too many electrons (30 instead of 26). Choice C is incorrect because it has too few protons (13 instead of 26). Choice D is incorrect because it has too few neutrons (43 instead of 30). Choice E is incorrect because it has too many neutrons (56 instead of 30) and electrons (26 instead of 30).

An Atom of the Element Iron Has an Atomic Number