This binary ionic compound consists of a cation and anion that both have 10 electrons. the charge of the anion is -1. You may find products containing this substance in your bathroom at home. What’s is the compounds name and formula?
Sodium fluoride = NaF
So what's the trick for answering this question? It's that both the anion and cation have 10 electrons!
An anion with 10e- and a charge of -1 must have 9 protons. That would make it the fluoride ion.
Here is a quick review of determining the number of subatomic particle in ions.
The video will also help you to understand why the positive ion is formed from sodium.
NaF is commonly added to municipal water supplies to help prevent tooth decay. In the early 1900's a dentist in Colorado named Frederick McKay discovered that many of his patients had a brown stain on their teeth which was caused by naturally occurring fluoride in the water they drank. The dentist also noted that the number of cavities these patients had was significantly lower than patients who did not have the Colorado brown stain. This discovery led to the practice of fluoridating water to help prevent tooth decay.
NaF is often added to toothpaste because of its ability to help prevent cavities. Apparently
Hope this helps!