Question

At first glance, it would seem that certain tetra fluoride $\left( {C{F_4}} \right)$ should be very similar to carbon tetrachloride $\left( {CC{l_4}} \right)$. Their name and their formula are very similar.
However, these molecules have different boiling points. The boiling point of $\left( {C{F_4}} \right)$ is 145 $K$, and the boiling point of $\left( {CC{l_4}} \right)$ is 350$K$.
Which of the following statements is the best explanation for this difference in boiling point?
A.The carbon tetrachloride molecule is larger and more polarized than the carbon tetrafluoride molecule.
B.The C-Cl bond is stronger and harder to break than C-F the bond.
C.Fluorine is more electronegative than chlorine, so the C-F bond is more polar than the C-Cl bond.
D.Carbon tetrachloride has the dipole-dipole forces, whereas carbon tetra fluoride only has London dispersion forces.

Answer 1

Chlorine and fluorine belong to the halogen family and as we move down the group the electronegativity decreases and the atomic size of the element increases due to the lesser effect of nuclear pull on the outer shells. Fluorine has a higher electronegativity than chlorine.

Complete step by step answer:
$CC{l_4}$: Carbon tetrachloride is a covalent compound composed of a central carbon atom attached with four chlorine atoms. It forms the tetrahedral structure with symmetry and has $sp_3$ hybridisation. It has its application as a dry cleaning agent, as refrigerant and solvent for fats and oils.
$C{F_4}$ : Chlorine fluoride is an interhalogen compound which is also known as tetrafluoromethane. The bond strength between $Cl$ and$F$, is quite high, providing the structure high bond strength due to the presence of multiple numbers of $Cl$ and $F$ bonds. The bond angle is of ${109^ \circ }28$ .It has its major application in refrigerators used at low temperatures, as a micro fabricator for electronic devices and as a detector for neutrons.
In chlorine$\left( {17} \right)$ the electronic configuration is as follows:
$1{s^{^2}}2{s^2}2{p^6}3{s^2}3{p^5}$
In fluorine $\left( 9 \right)$ the electronic configuration is as follows:
$1{s^{^2}}2{s^2}2{p^5}$
With these two electronic configurations we can see that the number of shells for chlorine are more as compared to fluorine, so the arrangement of electrons in chlorine will be easier making it polarized. Due to polarized nature $CC{l_4}$ has a high boiling point as compared to $C{F_4}$. The additional force which adds to high boiling point is London forces involved in $CC{l_4}$.
Thus the correct option is A i.e. The carbon tetrachloride molecule is larger and more polarized than the carbon tetrafluoride molecule.

Note:
London forces are the weak temporary attractive forces resulting when the electrons are arranged in such a manner that temporary dipole is induced. It is also known as induced dipole-induced dipole attraction.