Part 3 of Elements of ChemistryOne week.Manhattan apartment.Super-hot ex-boyfriend....What's the worst that could happen?It's been nine months since Kaitlyn Parker has seen or heard from Martin Sandeke—nine months and five stages of matter. She's lived through the worst of first-love heartbreak, and is most certainly stronger (and less likely to hide in science cabinets) than ever before.But now Martin is back. And he wants to be friends. But he's sending mixed signals to the Bunsen burner in Kaitlyn's pants.Will Martin re-capture Kaitlyn's heart? Can Kaitlyn and Martin ever be just friends? Or, despite an abundance of chemistry, are some bonds just too unstable to endure?