Question

What symbol would represent a chlorine ion with a stable arrangement of eight valence electrons?

Answer 1

Cl-
(The - needs to be at the top by the way)
This shows it has gained an electron to form a stable ion which gives it a negative charge (as there are now more electrons then protons)

:)

Answer 2

Cl⁻

Step-by-step explanation:

Elements in the periodic table (with the exception of group 0 elements) want to achieve there octet configuration and as such gain or lose electron(s) in order to achieve that. When an atom loses electron(s), it becomes positively charged and when it gains, it becomes negatively charged.

Chlorine (Cl) has 17 electrons.

₁₇Cl → 1S² 2S² 2P⁶ 3S² 3P⁵

From the above, it can be deduced that chlorine has 7 (5+2) electrons in its outermost shell and hence needs just one electron to achieve it's octet configuration. When chlorine gains this one electron it requires to achieve it's octet configuration, it becomes negatively charged (as explained earlier). Thus, it is represented as Cl⁻.