Carbide (C22-) ion contains only two carbon atoms. Each carbon atoms have -1 charge and there is a triple bond between carbon atoms. Also there is a lone pair on each carbon atom in C22- lewis structure.
Several characteristics of C22- lewis structure are mentioned below.
When we draw a lewis structure, there are several guidelines to follow. Number of steps can be changed according the complexity of the molecule or ion. However those all steps are mentioned and explained in detail in this tutorial to improve your knowledge about lewis structure drawing.
There is only one element in carbide ion; carbon. Carbon is a group IVA element in the periodic table and has four electrons in its last shell (valence shell).
Because, there is a -2 charge in carbide ion, two electrons should be added to total number of valence electrons.
Total valance electrons pairs = σ bonds + π bonds + lone pairs at valence shells
Total electron pairs are determined by dividing the number total valence electrons by two. For, carbide ion, total pairs of electrons are five (=10/2) in their valence shells.
because there is only two carbon atoms, no need to find center atom. Basic skeletal structure of carbide ion is given below.
After determining the center atom (did not need to do this for carbide ion) and skeletal of carbide ion, we can start to mark lone pairs on atoms. Remember that, there are total of five electron pairs.
There are charges on carbon atoms in above structure.
Because three are charges on both carbon atoms and having charges like -3 reduces the stability of molecule or ion. Therefore we need to do the step of reducing charges on atoms by converting lone pairs to bonds. Also. one carbon atom do not have eight electrons in its valence shell. Therefore , that structure is not stable whatsoever.
Now, we are going to convert one lone pair to a bond as following.
In the new structure too, there is -2 charge on one carbon atom and other carbon atom has not gained eight electrons in its valence shell.
Because distributing charges all over the molecule or ion will stable the molecule or ion, we can convert one more lone pair on carbon atom as below.
Questions
There are only two carbon atoms in carbide ion. Each carbon atom has -1 charge. Because, there are two carbon atoms, overall charge is -1*2 = -2
In carbide ion, oxidation of each carbon atom is -1. But, there is no rule to be have a same oxidation number and charge for an atom in a compound.
Charge of carbide ion is -2.