which of the following molecules is polar?
NO2
CO2
BF3
SF6
CCl4
dot and cross diagram of a molecule of HOCL
To do these properly you need to draw the Lewis electron dot structure and assign a shape to them. The shapes that are symmetrical are polar. The symmetrical shapes are not polar unless one of the binding sites is a different atom than then others. (For example, SF6 is octahedral and non-polar because it is symmetrical while SF5Cl is not symmetrical and is polar.)
NO2 is angular with an uneven number of electrons and is polar.
CO2 is linear and not polar.
BF3 is trigonal planar and not polar.
SF6 is Octahedral and is not polar.
CCl4 is tetrahedral and is not polar.
Which of the following molecules is the most polar? CCl4, H2O, BF3, CH4, NH4
To determine whether a molecule is polar or not, you need to consider the molecular geometry and the polarity of individual bonds within the molecule.
First, let's examine each molecule:
1. NO2: Nitrogen dioxide consists of one nitrogen (N) atom and two oxygen (O) atoms. If we draw out the Lewis structure, we can determine the shape:
O
|
N-O
According to the VSEPR (valence shell electron pair repulsion) theory, the molecule is bent, with a lone pair of electrons on the nitrogen atom. Since the N-O bonds are polar and the molecular geometry is not symmetrical, NO2 is a polar molecule.
2. CO2: Carbon dioxide has one central carbon (C) atom and two oxygen (O) atoms. The Lewis structure for CO2 is:
O=C=O
In this case, the molecule is linear, and the oxygen-carbon-oxygen bond angle is 180 degrees. Despite having polar bonds between carbon and oxygen, the symmetry of the molecule cancels out the polarity, making CO2 a nonpolar molecule.
3. BF3: Boron trifluoride contains one central boron (B) atom and three fluorine (F) atoms. The Lewis structure of BF3 is:
F
/
B-F-B
\
F
In this case, the molecule is trigonal planar, and all the B-F bonds are polar. However, due to the symmetrical molecular geometry, the polarities of the bonds cancel each other out, making BF3 a nonpolar molecule.
4. SF6: Sulfur hexafluoride consists of one central sulfur (S) atom and six fluorine (F) atoms. The Lewis structure for SF6 is:
F
/
F-S-F
\
F
|
F
In this case, the molecule adopts an octahedral shape, and all the S-F bonds are polar. Similar to BF3, the symmetry of the molecule causes the polarities to cancel each other out, resulting in SF6 also being a nonpolar molecule.
5. CCl4: Carbon tetrachloride is composed of one central carbon (C) atom and four chlorine (Cl) atoms. The Lewis structure for CCl4 is:
Cl
/
Cl-C-Cl
\
Cl
In this case, the molecule adopts a tetrahedral shape, and all the C-Cl bonds are polar. However, just like BF3 and SF6, the molecular geometry of CCl4 is symmetrical, leading to the cancellation of polarity. Therefore, CCl4 is a nonpolar molecule.
In summary, among the given molecules, only NO2 is polar. CO2, BF3, SF6, and CCl4 are all nonpolar. Remember, the polarity of a molecule is determined by both the existing polar bonds and the overall molecular geometry.