Which ion(s) has/have the same electron configuration (isoelectronic) as potassium?
1. ar-
2. rb+
3. si+
answer choices:
a. 2 and 3
b. 1
c. 1 and 3
d. all

The correct answer to your question is: b. 1

Explanation:

1. Ar-  This option is correct because the atomic number of Ar is 18, is one electron is added, it acquires a negative charge that is the charge shown next to the Ar symbol  and will have the same electron configuration that K has (atomic number 19).

2. Rb+  If Rb loses one electron it acquires a positive charge but the atomic number of Rb is 37 very far from the atomic number of potassium (K) which atomic number is 19.

3. Si+ Silicon has an atomic number of 14 very far from the atomic number of potassium, this option is incorrect.

im pretty sure its b