Chloroform (CHCl3) contains one carbon atom, three chlorine atoms and one hydrogen atom. In the lewis structure of CHCl3, carbon atom is located as the center atom and other atoms have made bonds with carbon atom.
There are three chlorine atoms around center carbon atom. Hydrogen atom has made a single bond with carbon atom and each chlorine atom has three lone pairs on their valence shell. As well, there are no charges on atoms in CHCl3 lewis structure.
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 for your knowledge.
There are three elements in chloroform; carbon, hydrogen and chlorine. Hydrogen is a group IA element in the periodic table and only has one electron in its last shell (valence shell).Carbon is a group IVA element in the periodic table and has four electrons in its last shell (valence shell). Also, Chlorine is a group VIIA element in the periodic table and contains seven electrons in its last shell. Now, we know how many electrons are there in valence shells of hydrogen, carbon and chlorine atoms.
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, CHCl3, Total pairs of electrons are thirteen in their valence shells.
Hydrogen atom cannot be a center atom because hydrogen can only keep two electrons in last shell.
Because, carbon can show higher valance than oxygen, carbon has the higher chance to be the center atom in CHCl3. Also, carbon is more electropositive than oxygen, it again proves, carbon should be the center atom in CHCl3.
After determining the center atom and sketch of CHCl3 molecule, we can start to mark lone pairs on atoms. Remember that, there are total of thirteen electron pairs.
There are no charges on atoms in above structure.
Because three are no charges on atoms, we do not need to do the step of reducing charges on atoms by converting lone pairs to bonds.
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