To determine the number of protons, neutrons, and electrons in the ion [tex]\({ }_{20}^{46} Ca ^{2+}\)[/tex], follow these steps:
1. Identify the Number of Protons:
- The subscript of the ion ([tex]\(_{20}\)[/tex]) indicates the atomic number, which is the number of protons in the nucleus. Therefore, this ion has 20 protons.
2. Calculate the Number of Neutrons:
- The superscript of the ion ([tex]\(^{46}\)[/tex]) represents the mass number, which is the total number of protons and neutrons.
- Subtract the number of protons from the mass number to find the number of neutrons:
[tex]\[
\text{Number of neutrons} = 46 - 20 = 26
\][/tex]
3. Determine the Number of Electrons:
- For a neutral atom, the number of electrons is equal to the number of protons.
- However, this is a [tex]\(2+\)[/tex] ion, meaning it has lost 2 electrons. Therefore, the number of electrons is:
[tex]\[
\text{Number of electrons} = 20 - 2 = 18
\][/tex]
Summarizing these calculations, the ion [tex]\({ }_{20}^{46} Ca ^{2+}\)[/tex] has:
- 20 protons,
- 26 neutrons, and
- 18 electrons.
Therefore, the correct choice is:
[tex]\[
\boxed{20\ p^*,\ 26\ n^0,\ 18\ e}
\][/tex]
