Question

Among the following the total number of polar molecules are_______
$C{l_2}$ , $OCl$ , $B{F_3}$ , $NO$ , $S{O_2}$ , $Xe{F_4}$ , $OCS$ , ${H_2}CC{l_2}$

Answer 1

Hint:
A polar compound usually has a negative partial charge and a positive partial charge. It is found in the compound that has one electronegative atom and an electropositive atom. The compound that is more electronegative will have a higher electron density.

Complete answer:
A polar bond is usually formed between two atoms that have different electronegativities. Polar bonds are usually seen in covalent bonds. A covalent bond is said to be polar when one atom has a greater electronegativity than the other atom. This means that the atom with the higher electronegativity will have a greater tendency to attract the shared pairs of electrons towards itself. This also implies that there will be more electron density towards this side of the bond. Thus, the more electronegative atom attains a negative partial charge. The less electronegative atom will attain a more positive partial charge since the electron density on this side decreases.
In the compounds given above, we can see which atoms in the molecule are more electronegative.
In the first compound: $C{l_2}$ , we can see that both the atoms are of the same kind. This means that the electronegativity of both the constituents is the same. Thus, we can say that $C{l_2}$ is Non Polar.
The next compound, $OCl$ is made of one chlorine and one oxygen atom. In this compound, the oxygen is more electronegative than chlorine. Therefore, $OCl$ is Polar.
$B{F_3}$ contains three fluorine atoms. But these fluorine toms are placed in space in such a way that it has trigonal planar geometry. This means that the bond vectors formed between the boron and fluorine can be combined into two resultant vectors which are in directions opposite to each other. Therefore, they will cancel each other out. Thus, we can say that $B{F_3}$ is a Non polar compound.
$NO$ has nitrogen and oxygen. Oxygen is more electronegative. Therefore, it is a Polar Compound.
$S{O_2}$ has the trigonal pyramidal structure and therefore, the bond vectors will not cancel each other. Therefore, $S{O_2}$ is Polar.
$Xe{F_4}$ contains the square planar geometry and also distributes its electrons symmetrically throughout the compound. This means that it is Non Polar.
$OCS$ contains oxygen, carbon and sulphur molecules. Therefore, the compound will be Polar.
${H_2}CC{l_2}$ contains two different bond vectors. There are a total of four bonds in this compound but out of them, two bonds are formed between hydrogen and carbon and two are formed between chlorine and carbon. These two similar bond vectors combine with themselves and forma a resultant bond between carbon and hydrogen and another resultant bond between carbon and chlorine. But we know that chlorine is highly negative. Therefore ${H_2}CC{l_2}$ will be Polar.
Therefore, the answer will be $5$ compound. That is, $OCl$ , ${H_2}CC{l_2}$ , $OCS$ , $NO$ , $S{O_2}$ .

Note: The polarity of a bond depends on the difference in electronegativity in case of diatomic or polyatomic compounds. It also depends on the geometry that is present in the compound in the case of polyatomic compounds.