Covalent Bonding and Electron Shells: Definitions, Relationship & the Octet Rule

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  • 0:06 Energy Levels
  • 1:15 Octet Rule
  • 2:18 Covalent Bonds
  • 3:13 Properties of Covalent…
  • 4:10 Lesson Summary
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Lesson Transcript
Instructor: Amy Meyers

Amy holds a Master of Science. She has taught science at the high school and college levels.

Learn about the different electron shells of atoms as well as the octet rule for valence electrons and how that applies to covalent bonding. Discover the definition of covalent bonding and the relationships between atoms.

Energy Levels

The octet rule states that atoms strive to have eight electrons in their outer shells
Octet Rule

Before we start this lesson, let's refresh your memory a bit with things you may know or things you may remember hearing about. Atoms are composed of protons and neutrons that live in the nucleus and electrons that orbit the nucleus in energy levels. Most atoms are combined into molecules. A molecule is a neutrally charged group of atoms that is held together by covalent bonds.

Electrons orbit the nucleus of an atom in energy levels or shells. In all but the smallest atoms, the outer energy shell likes to have eight electrons in it. Atoms love to have their outer shells filled with eight electrons. This is called the octet rule. If an atom doesn't have its outer shell full of eight electrons naturally, it will try to fill it by bonding with other atoms. Sometimes an atom will lose an electron or two or three in order to have its outer shell full. Sometimes it gains electrons. It all depends on what's easier. If there are only two electrons in the outer shell, it is easier to lose two than to gain six. If it loses two electrons, the lower shell, which is now the outer shell, will still be full, so it is still happy.

Octet Rule

Atoms like to be stable. They go to great lengths to be stable and happy. Stability to an atom is a complete outer energy level. The outer energy level is full of the valence electrons. Valence electrons are the electrons in the highest occupied energy level of an atom. The number of valence electrons mostly determines the properties of an element.

An octet is a set of eight: think octopus (an animal with eight legs) or octagon (a figure with eight sides). In chemistry, the octet rule says that atoms like to have full outer shells of only eight electrons. Atoms will lose or gain valence electrons to make their outer shells full with eight electrons, and they do this by bonding with other atoms. Those atoms can be the same element, as when oxygen bonds with itself to form O2, or with different elements, such as water, H2O. The exceptions to the octet rule are hydrogen and helium, which are both happy with two electrons in their outer shells.

Valence electrons are the electrons that form chemical bonds
Valence Electrons

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