What happens in a chemical reaction with the individual elements?

Chemical reactions involve electrons and where they move (if they move).
Metal atoms (or elements) usually give away their outer shell electrons in reactions to become stabilised (creating positive ions). Non-metal atoms (or elements) usually gain electrons in order to become stable (negative ions). Some reactions involve covalent bonds, metallic bonds, ionic bonds etc., but at the base (no pun intended :D) of most chemical reactions it's just a matter of electrons moving around between atoms.

Hope it helps! 

Cr(oh)3 -> cr(3+) + 3oh-