Question

What would the chemical formula of the compound look like if you combined Calcium and Iodine?

Answer 1

The formation reaction is:

`Ca(s) + I_2(s) rarr CaI_2(s)`

Explanation:

`Ca(s) + I_2(s) rarr CaI_2(s)`

This is in fact a redox reaction: calcium metal metal is oxidized up to `Ca^(2+)`, and `I_2` is reduced to iodide anion.

How do you know this occurs save by memory? Another way is to consider their positions in the Periodic Table. Calcium is a Group 2 metal, that has 2 valence electrons; its reactivity is chatacterized by its tendency to LOSE its valence electrons to form the `Ca^(2+)` ion. And iodine, as an oxidizing Group 17 non-metal, tends to GAIN electrons to form the iodide ion, `I^-`. Electrical neutrality demands that the salt of `Ca^(2+)` and `I^-` form an a `1:2` ratio. Why?