It’s positive when you use energy for work
- See charge on ion is -1 .
Hence it has taken 1 electron
Now first look at EC of Fluorine(F)

- Now one electron added .hence no of electrons is 10now
Look at the EC

Or
![\\ \bull\sf\dashrightarrow [He]](https://tex.z-dn.net/?f=%5C%5C%20%5Cbull%5Csf%5Cdashrightarrow%20%5BHe%5D)
Option C is correct.
Answer:
calcium ca
Explanation:
We can see here that the only element that is on the same group (column) as Ba (Barium) is Calcium (Ca).
Probably, above 100 Degree Celsius.
Mg gained mass because it went from being a single element (on the reactant side) to being a molecule (on the product side).