Chemical Bonds I: Covalent

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  • 0:15 Valence Electrons
  • 1:34 Covalent Bonds
  • 3:20 Multiple Bonds
  • 4:05 Molecule Structure
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Lesson Transcript
Instructor: Greg Chin
Mom always said that sharing is caring. This lesson will explore how electrons affect the chemical reactivity of atoms and specifically the merits of sharing electrons.

Valence Electrons

We've talked before about valence electrons and how valence electrons are important in determining the chemical reactivity of different types of atoms. Just as a reminder about atoms that have an incomplete valence shell - for instance, if this is an atom with one electron in its first shell, this atom isn't stable, and it wants to do all it can in order to stabilize its energy. There are basically three different ways that an atom might try to create a full valence level:

1) It could try to add electrons.

2) It could try to give away electrons.

3) It just might decide to share electrons.

This sharing strategy is what we're going to talk about today.

Making a Molecule

When an atom interacts with another atom, it forms what is called a chemical bond. This interaction, this chemical bond links the two atoms together into something called a molecule.

Making a Covalent Bond

Now, we're going to be talking about covalent bonds, which means that the atoms are going to share electrons. Covalent bonds are very strong bonds. They're very important in biology because they're very stable and because most biological molecules are made with covalent bonds. These biological molecules are then very stable.

So, atoms with more than one valence electron - let's take Carbon for example. Carbon has four valence electrons, so it has the opportunity to form four different covalent bonds.

Diagram of a carbon atom
Carbon Diagram

So, I can have it bond with hydrogen, and hydrogen will provide one electron of its own. The hydrogens are basically sharing electrons, so it has two valence electrons. And, the carbon atom, instead of having four, now has eight valence electrons.

Four bonds that carbon can form with hydrogens
Covalent Bond Illustration

Both the carbon and the hydrogen have stabilized their valence levels by sharing electrons. Instead of a dot representation, the bond between these atoms is often abbreviated with a line. So I can draw the four bonds that carbon can form with these hydrogens like this.

Diagram of a single covalent bond
Single Covalent Bond

Now, because carbon has four valence electrons, it can form four different bonds. It's possible to form multiple bonds with the same partner atom if that atom also has enough valence electrons for that to happen.

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