#### Answer

a) Element - Phosphorus (P)
Number of protons = 15
Number of neutrons = 16
b) Element - Iodine (I)
Number of protons = 53
Number of neutrons = 74
c) Element - Potassium (K)
Number of protons = 19
Number of neutrons = 20
d) Element - Ytterbium (Yb)
Number of protons = 70
Number of neutrons = 103

#### Work Step by Step

a) Mass number = A = 31
Atomic number = Z = 15
So the atom with atomic number 15 is Phosphorus (P)
Thus, number of protons = Atomic number = Z = 15
Also, number of neutrons = A - Z = 31 - 15 = 16.
b) Mass number = A = 127
Atomic number = Z = 53
So the atom with atomic number 53 is Iodine (I)
Thus, number of protons = Atomic number = Z = 53
Also, number of neutrons = A - Z = 127 - 53 = 74.
c) Mass number = A = 39
Atomic number = Z = 19
So the atom with atomic number 19 is Potassium (K)
Thus, number of protons = Atomic number = Z = 19
Also, number of neutrons = A - Z = 39 - 19 = 20.
d) Mass number = A = 173
Atomic number = Z = 70
So the atom with atomic number 70 is Ytterbium (Yb)
Thus, number of protons = Atomic number = Z = 70
Also, number of neutrons = A - Z = 173 - 70 = 103.