How do you draw double and triple bonds in Lewis Symbols?

1 Answer
anor277
Dec 17, 2016

Let's look at 2 small molecules: "acetylene"; and "hydrogen cyanide".

Explanation:

Both molecules contain formal triple bonds.

"Acetylene:" C_2H_2; there are 2xx4(C)+2(H) "valence electrons", thus 10 valence electrons to distribute.

H-C-=C-H

"Hydrogen cyanide:" HCN; there are 4(C)+5(N)+1(H) "valence electrons", thus 10 valence electrons to distribute.

H-C-=N:

At the nitrogen centre 2 of the valence electrons are lone-pair, and thus the nitrogen is associated with 2("inner shell")+2("lone pair)"+3("C-N triple bond)= 7 electrons", whose charge is balanced by the 7 protons in the nitrogen nucleus. Are you happy with this?

Can you similarly account for the bonding in "ethylene", H_2C=CH_2, with "12 valence electrons"?

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