hoe de we know when there should be a double bond while making a lewis dot structure?

hoe de we know when there should be a double bond while making a lewis dot structure?


1 Answers

Ramesh V
70 Points
14 years ago

The number of valence electrons on a single O is 6. If two O's were to bond, then there should be a double bond present. A bond counts as two electrons and since it's a double bond, it already counts as four electrons being shared. At this point each O would have four unshared electrons each. Since both of them share four electrons and have another four unshared, the system follows the octet rule.

N has 5 valence electrons. If you use a double bond, the result would be four shared electrons and three unshared for each N. That would only sum up to seven and is obviously not following the octet rule. Hence, a triple bond is used.

H has only 1 valence electron and since we're bonding two H's, that amounts to a total of two. We can't have a double bond 'cause the H's can't share more than 1 electron each. That's why only a single bond occurs. And, if you check the number of electrons each, they'd follow the octet rule.

NOTE: For H doesn't need 8 electrons in it's valence shell to be stable. It only requires 2; the same number of valence electrons He (helium) has


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Naga Ramesh
IIT Kgp - 2005 batch

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