Do you ever watch cheesy romantic comedies? Don't worry. We won't tell. The guy in the movie usually says something like, "I don't want to live without you," or, "You complete me," or, "Milk was a bad choice." Well, not that last line, but you get the idea. Believe it or not, the characters in romantic comedies are similar to elements when forming that "perfect bond."
People tend to look for stability by forming long lasting relationships with other people. So do elements. Even though we may look for qualities like sense of humor, intelligence, or mega hotness, atoms don't care about any of that stuff. They only have a weakness for one thing: money. (Not really.) Atoms have a thing for electrons.
Atoms have a one-track mind when it comes to electrons. Valence electrons are particularly high on their list of importance. They reside in the outermost shell at the highest energy level. These electrons will determine the reactivity of an element. Atoms will tend to gain, lose, or share valence electrons in order to achieve stability. If an atom has unpaired electrons in its outer shell, then that atom is on the dating market and considered to be super hot. We mean hot in an attractive way, not in the temperature way. The temperature of atoms is a whole different lesson.