Let's determine the correct isotope notation for an ion with 19 protons, 20 neutrons, and 18 electrons, following these steps:
1. Determine the Atomic Number (Z):
- The atomic number [tex]\( Z \)[/tex] is the number of protons in the nucleus. Therefore, for this ion:
[tex]\[
Z = 19
\][/tex]
- This atomic number corresponds to the element Potassium ([tex]\( K \)[/tex]) on the periodic table.
2. Calculate the Mass Number (A):
- The mass number [tex]\( A \)[/tex] is the sum of protons and neutrons. Therefore:
[tex]\[
A = \text{Protons} + \text{Neutrons} = 19 + 20 = 39
\][/tex]
3. Determine the Charge of the Ion:
- The charge of the ion is determined by the difference between the number of protons and electrons. Since the ion has 19 protons and 18 electrons:
[tex]\[
\text{Charge} = \text{Protons} - \text{Electrons} = 19 - 18 = +1
\][/tex]
4. Write the Isotope Notation:
- The isotope notation is written with the mass number as a superscript to the left of the element symbol, the atomic number as a subscript to the left of the element symbol, and the charge as a superscript to the right of the element symbol.
Therefore, the correct isotope notation for the given ion is:
[tex]\[
{}_{19}^{39} K^{+1}
\][/tex]
Out of the provided options, this corresponds to:
[tex]\[
{}_{19}^{39} K^{+1}
\][/tex]
