General Chemistry

Carbon tetrafluoride (CF4) is a molecule that consists of one carbon atom and four fluorine atoms. To determine the bond angle in CF4, we must first understand its molecular geometry. Step 1: Determine the Lewis Structure The first step in predicting the molecular geometry is to draw the Lewis structure of the molecule. Carbon has four valence electrons, and each fluorine atom has seven valence electrons, for a total of \(4 + (4 \times 7) = 32\) valence electrons. In the Lewis structure, carbon is the central atom with four fluorine atoms surrounding it. Each fluorine atom forms a single bond with the carbon atom, using up 8 electrons (4 bonds × 2 electrons per bond). The remaining 24 electrons (32 total valence electrons - 8 electrons in bonds) are distributed as lone pairs on the fluorine atoms, with each fluorine getting three lone pairs. Step 2: Predict the Molecular Geometry Using VSEPR Theory The Valence Shell Electron Pair Repulsion (VSEPR) theory is used to predict the shape of the molecule. According to VSEPR theory, electron pairs around a central atom will arrange themselves as far apart as possible to minimize repulsion. In CF4, there are four bonding pairs and no lone pairs on the central carbon atom. This arrangement of electron pairs leads to a tetrahedral molecular geometry. Step 3: Determine the Bond Angles In a perfect tetrahedral molecule, the bond angles are 109.5 degrees. This is because the tetrahedral shape allows for the electron pairs to be as far apart as possible, minimizing repulsion. Since CF4 has a tetrahedral geometry, the bond angles between the carbon and fluorine atoms are approximately 109.5 degrees. Comparison to Other Tetrahedral Molecules: The bond angle in CF4 is similar to other tetrahedral molecules such as methane (CH4), silicon tetrachloride (SiCl4), and sulfur tetrafluoride (SF4) before considering any lone pair effects. However, if there are lone pairs present on the central atom, as in the case of ammonia (NH3) or water (H2O), the bond angles will be slightly less than 109.5 degrees due to the increased repulsion from the lone pairs. In summary, the bond angle in CF4 is approximately 109.5 degrees, which is characteristic of a tetrahedral molecular geometry. This bond angle is consistent with other tetrahedral molecules that have no lone pairs on the central atom.

Question

What is the CF4 bond angle, and how does it compare to other tetrahedral molecules?

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