Question

When drawing Lewis dot structures, what should you do if you run out of electrons before all atoms are satisfied?
A.Leave it as it is
B.Try double or triple bonds
C.Make a resonance structure
D.Add the missing electrons

Answer 1

Hint: Lewis symbols which are also known as Lewis dot diagrams or electron dot diagrams are diagrams that represent the valence electrons of an atom and their distribution. Lewis structures are diagrams that represent the valence electrons of atoms within a molecule and the bonds they form. These Lewis symbols and Lewis structures will help in visualizing the valence electrons of atoms and molecules, whether they exist in the molecule as lone pairs or within bonds.

Complete answer:
We should take care while drawing Lewis dot structures as to use all the electrons given to you. You should try inserting double or triple bonds if you run out of electrons before all atoms are satisfied in the given molecule. A very good example of this kind of situation is Hydrogen Cyanide molecule. There are a total of 10 valence electrons contributed by the hydrogen, carbon and nitrogen. Hydrogen has completed duplet and Nitrogen has completed octet. But Carbon is electron deficient. Hence, a triple bond between Carbon and Nitrogen is suggested by the Lewis structure.

Hence option (B) is the correct answer.

Note:
It is sometimes very useful to calculate the formal charge on each atom in the molecule by using the Lewis structure of that molecule. The first step in calculating the formal charge involves dividing the electrons in each covalent bond between the atoms that form the bond in that molecule. If the atom has more valence electrons than the neutral atom, it is assumed to carry a formal charge of -1. If it has fewer electrons as the valence electrons then it is assigned a formal positive charge.