Here's how to figure out the number of electrons in the outermost energy level of a chloride ion:

1. Understanding the Basics

* Neutral Chlorine Atom: A neutral chlorine atom (Cl) has 17 electrons. Its electron configuration is 2-8-7, meaning it has 7 electrons in its outermost energy level (the third energy level).

* Chloride Ion (Cl-) : A chloride ion is formed when a chlorine atom gains one electron. This extra electron fills the outermost energy level, making it a stable octet.

2. The Answer

A chloride ion (Cl-) has 8 electrons in its outermost energy level.