Polar Bonds and Molecular Shape
A polar molecule is a molecule that has a net dipole moment due to its having unsymmetrical polar bonds. There are two factors that go into determining if a molecule is polar or not. To determine if a molecule (or ion) is polar or non-polar, you must determine both factors.
First, to determine if a given individual bond is polar, you need to know the electronegativity of the two atoms involved in that bond. To find the electronegativities of all the elements, look at the Periodic Table (follow the link below this answer under Web Links).
If the electronegativity of the two atoms has a difference of 0.3 or less, then the bond is non-polar. If the electronegativity difference is greater that 0.3 but less than 1.7, then the bond is polar. If the two values have a difference greater than 1.7, then the bond is ionic, which is just very very polar.
Once you know which bonds in the molecule are polar and which are non-polar, you must use the shape of the molecule. You need the shape because two polar bonds, if oriented correctly can cancel each other out (like two equally strong people pulling in opposite directions on a rope -- nobody moves).
The three possible outcomes:
Lactic acid is a polar molecule. It contains both polar (-OH) and nonpolar (CH3) groups, but the presence of the polar -OH groups makes it an overall polar molecule.
The relationship between bond polarity and molecular polarity is that the overall polarity of a molecule is determined by the polarity of its individual bonds. If a molecule has polar bonds that are not symmetrical, the molecule will be polar overall. If a molecule has nonpolar bonds or symmetrical polar bonds that cancel each other out, the molecule will be nonpolar overall.
One way to determine if a molecule is polar or nonpolar without relying on electronegativity values is to consider its molecular geometry. If a molecule has a symmetrical shape and the individual bond dipoles cancel each other out, then the molecule is nonpolar. On the other hand, if the molecule has an asymmetrical shape and the bond dipoles do not cancel out, then the molecule is polar.
Fe2O3 (iron oxide) is a nonpolar molecule because it has a symmetrical arrangement of its polar covalent bonds. The dipole moments in these bonds cancel each other out, resulting in a nonpolar overall molecule.
CH3Br is a nonpolar molecule. Although the C-Br bond is polar due to the electronegativity difference between carbon and bromine, the overall molecule is nonpolar because of its symmetrical tetrahedral molecular geometry.
Lactic acid is a polar molecule. It contains both polar (-OH) and nonpolar (CH3) groups, but the presence of the polar -OH groups makes it an overall polar molecule.
Check the molecular geometry to determine if the molecule is asymmetrical. If the molecule has a symmetrical shape, it is likely nonpolar. If it is asymmetrical, check for polar bonds and the overall molecular polarity.
The relationship between bond polarity and molecular polarity is that the overall polarity of a molecule is determined by the polarity of its individual bonds. If a molecule has polar bonds that are not symmetrical, the molecule will be polar overall. If a molecule has nonpolar bonds or symmetrical polar bonds that cancel each other out, the molecule will be nonpolar overall.
One way to determine if a molecule is polar or nonpolar without relying on electronegativity values is to consider its molecular geometry. If a molecule has a symmetrical shape and the individual bond dipoles cancel each other out, then the molecule is nonpolar. On the other hand, if the molecule has an asymmetrical shape and the bond dipoles do not cancel out, then the molecule is polar.
Yes, a molecule can be nonpolar when it contains polar covalent bonds, because think about it. if the molecule is linear in structure, and it has two equally polar bonds on either side, then the polarity will essentially cancel out, and it will become nonpolar.
Fe2O3 (iron oxide) is a nonpolar molecule because it has a symmetrical arrangement of its polar covalent bonds. The dipole moments in these bonds cancel each other out, resulting in a nonpolar overall molecule.
CH3Br is a nonpolar molecule. Although the C-Br bond is polar due to the electronegativity difference between carbon and bromine, the overall molecule is nonpolar because of its symmetrical tetrahedral molecular geometry.
One can determine if a bond is polar or nonpolar by looking at the symmetry of the molecule. If the molecule is symmetrical and the atoms on either side of the bond are the same, the bond is likely nonpolar. If the molecule is asymmetrical or the atoms on either side of the bond are different, the bond is likely polar.
The molecule is nonpolar.
Molecular polarity is determined by the overall arrangement of polar bonds within a molecule. If a molecule has polar bonds that are arranged symmetrically, the molecule is nonpolar. However, if the polar bonds are arranged asymmetrically, the molecule is polar. Therefore, the relationship between molecular polarity and bond polarity is that the presence and arrangement of polar bonds within a molecule determine its overall polarity.
No a molecule is a molecule, polar or nonpolar.
Phenyl salicylate has covalent bonds, which are typically nonpolar. The molecule is symmetrical and contains nonpolar functional groups, making it nonpolar overall.