To draw the Lewis structure for carbon disulfide (CS2), we start by determining the total number of valence electrons available for bonding. Carbon (C) has 4 valence electrons, and each sulfur (S) atom has 6 valence electrons. Therefore, the total for CS2 is:
- 4 (from C) + 6 (from S) + 6 (from S) = 16 valence electrons.
Next, we place the carbon atom in the center because it is the least electronegative, and the two sulfur atoms surrounding it:
S
C
S
Now, we will form bonds between the central carbon atom and each sulfur atom. Each single bond accounts for 2 electrons. By placing a double bond between carbon and each sulfur, we distribute the electrons as follows:
Each C=S double bond uses 4 electrons, so we use 8 electrons of the total 16. This leaves us with 8 electrons left, which we will use to complete the octets of the sulfur atoms. The completed Lewis structure looks like this:
..S= C = S..
Each sulfur now has a full octet, and the carbon atom also has 8 electrons in its valence shell due to the two double bonds.
Now, focusing on the geometry, we consider the electron pair geometry at the central carbon atom. It has no lone pairs of electrons and forms two double bonds. The arrangement of these bonds results in:
- Electron Pair Geometry: Linear.
- Molecular Geometry: Linear as well.
This linear geometry arises because the repulsion between the bonded pairs is minimized when they are 180° apart from each other. Therefore, both the electron pair and molecular geometries around the central carbon atom in CS2 are linear.