Given the formula 4f10, what does the 10 stand for?

Iknow #2 is d. i just need to know why

What is the correct lewis structure for chloroform chcl3

What is the chemical name of the compound na2co3? use the list of polyatomic ions and the periodic table to you answer. a. sodium carbon oxide b. sodium carbonate c. sodium(ll) carbonate d. sodium oxalate