© 2014 Shmoop University, Inc. All rights reserved.
 

Topics

The Octet Rule

The valence electrons follow something called the octet rule. According to the octet rule, atoms achieve stability once they have a full valence shell (which is 8 electrons in most cases). Once they have eight electrons in their valence shell they feel complete. If only we could fix everything that simply. "Your laptop is broken? Just add these two electrons and it will be fine."

Let's say you rent a limo to take you and your friends to prom. The limo has eight seats and it cost a pretty penny to rent. You need to invite only your date and three other couples to ride in it. If you have more than eight, the limo won't be comfortable to sit in. If you invite less people then the limo will cost more per person. Therefore, you need exactly eight people in your limo to hit the sweet spot. This situation is like the bonding of atoms. In an atom's outer shell (the limo) each atom needs exactly eight electrons (fellow riders).

There are three types of bonds that will be further discussed in this module. Here are some guidelines to help you remember them:

Metals + Nonmetals → Ionic Bonds
Nonmetal + Nonmetal → Covalent Bonds
Metal + Metal → Metallic Bonds

As we have said, bonding happens when an atom needs to complete its outer shell. This could mean losing, gaining, or sharing electrons. Once the outer shell is complete, the atom becomes isoelectronic. This means they have the same number and arrangement of electrons as the closest noble gas (group VIIIA). Remember noble gases are extremely stable due to their filled outer shell (8 valence electrons). That's why they get to take a limo to prom.

You don't like the idea of a limo filled with noble gasses? Well, let's move on then.

Ever wanted to predict the future like The Oracle? Now could be your chance. You heard us right. With the proper training and the right conditions, even you can predict how an element will react with other elements and what types of compounds it will form. All it takes is to know what's going on in the atom's orbitals in order to predict how it will react. (We cannot guarantee you will predict lottery numbers.)

Electron Configuration is the arrangement of the electrons in a particular atom or element. This is without a doubt the best kept secret for predicting the fate of an atom—so keep it to yourself. Just kidding. You can tell people.

Wait, you're not impressed? Well, what if we could predict the shape or geometry of the molecular substance too? Does that pique your interest? Calm down. There is a way, and we're about to show it to you.

According to the Valence Shell Electron Pair Repulsion (VSEPR) theory the shape formed by a molecule is based on the valence electrons surrounding the central atom. A molecule can form many different shapes depending on the types and number of atoms involved. Atoms are like nature's Legos and we're about to learn how to snap them together.
Advertisement
Advertisement
back to top