Answer :

To determine the number of protons, neutrons, and electrons in the [tex]\(^{99}_{40}\text{Zr}^{2+}\)[/tex] ion, let's break it down step-by-step.

1. Atomic Number and Protons:
- The atomic number of zirconium (Zr) is 40. This number represents the number of protons in the nucleus of the atom.
- Therefore, the number of protons in [tex]\(^{99}_{40}\text{Zr}^{2+}\)[/tex] is 40.

2. Mass Number and Neutrons:
- The mass number of this isotope of zirconium is 99. The mass number is the sum of the number of protons and neutrons.
- Since we already know there are 40 protons, we can find the number of neutrons by subtracting the number of protons from the mass number.
- Neutrons = Mass number - Number of protons = 99 - 40 = 59
- Therefore, the number of neutrons in [tex]\(^{99}_{40}\text{Zr}^{2+}\)[/tex] is 59.

3. Charge and Electrons:
- The given ion has a [tex]\(2+\)[/tex] charge, meaning it has lost 2 electrons.
- In a neutral zirconium atom, the number of electrons equals the number of protons, which is 40.
- Since the [tex]\(^{99}_{40}\text{Zr}^{2+}\)[/tex] ion has a [tex]\(2+\)[/tex] charge, it has 2 fewer electrons than the neutral atom.
- Electrons = Number of protons - Charge = 40 - 2 = 38
- Therefore, the number of electrons in [tex]\(^{99}_{40}\text{Zr}^{2+}\)[/tex] is 38.

In summary:
- The number of protons is 40.
- The number of neutrons is 59.
- The number of electrons is 38.