for each of the molecules below, show the dipole you would expect. you must show the direction of the dipole - arrow head pointing toward the negative end.
1) CF4
2) CH3Cl
Look at the electronegativities(EN). That will tell you how to draw the arrow.
The EN of C is about 2.5 and that of H is about 2.1 so H is the + end and C is the arrow head.
To determine the dipole moment for each of the molecules, you need to consider the polarity of the individual bonds and the molecular geometry.
1) CF4:
First, you need to determine the Lewis structure of CF4. Carbon (C) is the central atom and has four fluorine (F) atoms attached to it. Carbon has four valence electrons, and fluorine has seven valence electrons.
The Lewis structure for CF4 is:
F F
\ /
C
/ \
F F
In CF4, the dipole moments of the four C-F bonds cancel each other out due to the symmetric tetrahedral geometry around the carbon atom. This means CF4 is a nonpolar molecule, and there is no dipole moment expected.
2) CH3Cl:
Again, you need to determine the Lewis structure for CH3Cl. Carbon (C) is the central atom, and hydrogen (H) and chlorine (Cl) atoms are attached to it. Carbon has four valence electrons, hydrogen has one valence electron, and chlorine has seven valence electrons.
The Lewis structure for CH3Cl is:
H Cl
| |
H-C-H
|
H
In CH3Cl, the dipole moment of the C-Cl bond does not cancel with the dipole moments of the C-H bonds because of the molecular geometry. The chloromethane molecule has a trigonal pyramidal shape with a lone pair on the central carbon atom, causing an uneven distribution of electron density.
The dipole moment of the C-Cl bond points toward the chlorine atom as the more electronegative atom. The dipole moment of the C-H bonds points away from the carbon atom towards the hydrogen atoms.
Therefore, the dipole moment in CH3Cl points from the carbon atom towards the chlorine atom.