#### Answer

a. 143 neutrons, 92 protons, 92 electrons
b. 14 neutrons, 13 protons, 13 electrons
c. 31 neutrons, 26 protons, 26 electrons
d. 126 neutrons, 82 protons, 82 electrons
e. 49 neutrons, 37 protons, 37 electrons
f. 21 neutrons, 20 protons, 20 electrons

#### Work Step by Step

If we are given an atom's mass number and atomic number, then we can find out how many protons, neutrons, and electrons that particular atom contains. We can find the atom's atomic number by looking at the periodic table. The atomic number is also the number of protons in an atom. The mass number is the sum of the number of protons and the number of neutrons in the atom. We subtract the atomic number, which is also the number of protons, from the mass number to get the number of neutrons in that particular atom. In an uncharged atom, the number of protons and electrons are equal.
a. The mass number of this atom of uranium is 235. If we subtract the atomic number of uranium, 92, from this mass number, we get 143, which is the number of neutrons. The number of electrons and protons are the same as the atomic number in a neutral or uncharged atom; therefore, there are 92 protons and 92 electrons in this atom of uranium.
b. The mass number of this atom of aluminum is 27. If we subtract the atomic number of aluminum, 13, from this mass number, we get 14, which is the number of neutrons. The number of electrons and protons are the same as the atomic number in a neutral or uncharged atom; therefore, there are 13 protons and 13 electrons in this atom of aluminum.
c. The mass number of this atom of iron is 57. If we subtract the atomic number of iron, 26, from this mass number, we get 31, which is the number of neutrons. The number of electrons and protons are the same as the atomic number in a neutral or uncharged atom; therefore, there are 26 protons and 26 electrons in this atom of iron.
d. The mass number of this atom of lead is 208. If we subtract the atomic number of lead, 82, from this mass number, we get 126, which is the number of neutrons. The number of electrons and protons are the same as the atomic number in a neutral or uncharged atom; therefore, there are 82 protons and 82 electrons in this atom of lead.
e. The mass number of this atom of rubidium is 86. If we subtract the atomic number of rubidium, 37, from this mass number, we get 49, which is the number of neutrons. The number of electrons and protons are the same as the atomic number in a neutral or uncharged atom; therefore, there are 37 protons and 37 electrons in this atom of rubidium.
f. The mass number of this atom of calcium is 41. If we subtract the atomic number of calcium, 20, from this mass number, we get 21, which is the number of neutrons. The number of electrons and protons are the same as the atomic number in a neutral or uncharged atom; therefore, there are 20 protons and 20 electrons in this atom of calcium.