Chapter 2 - Atoms, Molecules, and Ions - Exercises - Page 76: 62

a) Uranium (235) $\Longrightarrow$ Number of protons = 92 $\Longrightarrow$ Number of electrons = 92 $\Longrightarrow$ Number of neutrons = 143 b) Aluminum (27) $\Longrightarrow$ Number of protons = 13 $\Longrightarrow$ Number of electrons = 13 $\Longrightarrow$ Number of neutrons = 14 c) Iron 57 $\Longrightarrow$ Number of protons = 26 $\Longrightarrow$ Number of electrons = 26 $\Longrightarrow$ Number of neutrons = 31 d) Lead (208) $\Longrightarrow$ Number of protons = 82 $\Longrightarrow$ Number of electrons = 82 $\Longrightarrow$ Number of neutrons = 126 e)Rubidium (86) $\Longrightarrow$ Number of protons = 37 $\Longrightarrow$ Number of electrons = 37 $\Longrightarrow$ Number of neutrons = 49 f) Calcium (41) $\Longrightarrow$ Number of protons = 20 $\Longrightarrow$ Number of electrons = 20 $\Longrightarrow$ Number of neutrons = 21

a) Uranium (235): Atomic number = Z = 92 Mass number = A = 235 Thus number of protons = Z = 92 If the atom is neutral, then number of electrons = number of protons. (Since the positive and negative charges on protons and electrons respectively are equal and thus cancel out each other) Thus number of electrons = Z = 92 Number of neutrons = A -Z = 235 - 92 = 143 b) Aluminum (27) Atomic number = Z = 13 Mass number = A = 27 Thus number of protons = Z = 13 If the atom is neutral, then number of electrons = number of protons. (Since the positive and negative charges on protons and electrons respectively are equal and thus cancel out each other) Thus number of electrons = Z = 13 Number of neutrons = A -Z = 27 - 13 = 14 c) Iron (57) Atomic number = Z = 26 Mass number = A = 57 Thus number of protons = Z = 26 If the atom is neutral, then number of electrons = number of protons. (Since the positive and negative charges on protons and electrons respectively are equal and thus cancel out each other) Thus number of electrons = Z = 26 Number of neutrons = A -Z = 57 - 26 = 31 d) Lead (208) Atomic number = Z = 82 Mass number = A = 208 Thus number of protons = Z = 82 If the atom is neutral, then number of electrons = number of protons. (Since the positive and negative charges on protons and electrons respectively are equal and thus cancel out each other) Thus number of electrons = Z = 82 Number of neutrons = A -Z = 208 - 82 = 126 e) Rubidium (86) Atomic number = Z = 37 Mass number = A = 86 Thus number of protons = Z = 37 If the atom is neutral, then number of electrons = number of protons. (Since the positive and negative charges on protons and electrons respectively are equal and thus cancel out each other) Thus number of electrons = Z = 37 Number of neutrons = A -Z = 86 - 37 = 49 f) Calcium (41) Atomic number = Z = 20 Mass number = A = 41 Thus number of protons = Z = 20 If the atom is neutral, then number of electrons = number of protons. (Since the positive and negative charges on protons and electrons respectively are equal and thus cancel out each other) Thus number of electrons = Z = 20 Number of neutrons = A -Z = 41 - 20 = 21