Question

Protons, Neutrons, Electrons for isotopes: Zirconium-90 and Antimony-123?

Answer 1

Atomic number=40
Atomic mass=91 Of Zr
Protons and neutrons are the same as atomic number so:
Protons=40
neutrons=91-40=51
Electron=40

Atomic number=51
Atomic mass=121.763 approximately 122 of SN
Protons=51
neutrons=122-51=71
electrons=51

Answer 2

Data:

z = p = e

Using:

Zirconium $Zr^{90}$ 

Atomic Mass (A) = 90
Atomic number (z) = 40
Neutron number (n) = ?

A = z + n
90 = 40 + n
n = 90 - 40
n = 50

Soon (Zirconium)
z = p = e
40 = 40 = 40

Protons (p) = 40
neutrons (n) = 50
Electrons (e) = 40

----------------------------------------------------
Using:

Antimony $Sb^{123}$ 

Atomic Mass (A) = 123
Atomic number (z) = 51
Neutron number (n) = ?

A = z + n
123 = 51 + n
n = 123 - 51
n = 72

Soon (Antimony)
z = p = e
51 = 51 = 51

Protons (p) = 51
neutrons (n) = 72
Electrons (e) = 51