Question Video: Calculating the Number of Covalent Bonds Possible from the Number of Valence Electrons Chemistry

The valence shell of oxygen is the second electron shell and contains 6 electrons. How many covalent bonds can oxygen form?

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Video Transcript

The valence shell of oxygen is the second electron shell and contains six electrons. How many covalent bonds can oxygen form?

The valence shell is the outermost electron shell. The electrons in the valence shell are the electrons that are involved in the formation of bonds and ions. This is because atoms will typically gain, lose, or share electrons and bonds so that they have a full outer shell, which is typically eight valence electrons. The problem tells us that oxygen has six valence electrons. But if the problem didn’t give us this information, we would be able to determine the number of valence electrons using the periodic table, since for main group elements, the number of valence electrons is consistent down a group.

Either way, since oxygen has six valence electrons, it will gain two electrons according to the octet rule so that it can have a full valence shell. It can do this by either forming an ion or by forming bonds. But this question specifically asked us about how many bonds oxygen can form. When atoms bond covalently, electrons are shared between atoms with each atom that’s participating in the bond, giving one of its electrons to the bond. So each covalent bond that an atom forms will effectively make it gain one electron. So oxygen can form two covalent bonds, which is what we see in molecules that oxygen forms when it bonds covalently, like H2O where oxygen is bonded to two hydrogens.

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