To draw the Lewis structure for carbon tetrabromide (CBr4), start by determining the total number of valence electrons in the molecule. Carbon (C) contributes 4 valence electrons, and each bromine (Br) contributes 7 valence electrons. Since there are four bromine atoms, the total is:
- 4 (from C) + 4 × 7 (from Br) = 4 + 28 = 32 valence electrons.
In the Lewis structure, carbon is the central atom surrounded by the four bromine atoms. Each bromine atom forms a single bond with the carbon atom, using 2 electrons per bond. Thus, 4 bonds consume 8 electrons, leaving us with 24 electrons. Each bromine atom needs 6 more electrons to complete their octets, totaling 24 electrons used, which fits with our calculation.
Now, let’s analyze the properties of CBr4:
- a. Number of Electron Groups: There are 4 electron groups around the central carbon atom (each C-Br bond counts as one group).
- b. Electron Pair Geometry: The electron pair geometry is tetrahedral, given there are four bonding pairs and no lone pairs on the carbon.
- c. Bond Angle: The ideal bond angle in a tetrahedral geometry is approximately 109.5 degrees.
- d. Number of Bonded Electrons: There are 8 bonded electrons (4 bonds × 2 electrons per bond).
- e. Molecular Geometry: The molecular geometry of CBr4 is also tetrahedral, as only bonding pairs are present.
- f. Polarity: CBr4 is nonpolar because the dipoles of the C-Br bonds cancel each other out due to its symmetrical tetrahedral shape.
In summary, CBr4 features a tetrahedral arrangement with specific bond angles, bonded electrons, and is classified as a nonpolar molecule.