Question

how many total electrons are in the o2- ion?
18
9
10
16
8
question 18
1 pts
which one of the following is a halogen?
phosphorous
argon
sodium
chlorine
helium

Explanation:

Step1: Find atomic number of oxygen

Oxygen has an atomic number of 8, which means a neutral oxygen atom has 8 electrons.

Step2: Consider the charge of the ion

The $O^{2 -}$ ion has a 2 - negative charge, meaning it has gained 2 electrons. So the total number of electrons is $8 + 2=10$.

Step3: Recall halogen elements

Halogens are elements in group 17 of the periodic table. Chlorine is in group 17, while phosphorous is in group 15, argon is a noble - gas in group 18, sodium is in group 1, and helium is a noble - gas in group 18.

Answer:

1. C. 10
2. D. chlorine