On the basis of strength of intermolecular forces, which of the following elements would be expected to have the highest melting point?
On the basis of strength of intermolecular forces, which of the following elements would be expected to have the highest melting point?
(A)# Br_2 #
(B) #Cl_2#
(C) #F_2#
(D) #Kr#
(E) #N_2#
I understand that LDF strength increases with increasing charge and increasing molecular size. Based on that, would not #Kr# has the strongest LDF and hence the highest melting point? Why is #N_2# the correct answer?
On the basis of strength of intermolecular forces, which of the following elements would be expected to have the highest melting point?
(A)
(B)
(C)
(D)
(E)
I understand that LDF strength increases with increasing charge and increasing molecular size. Based on that, would not
1 Answer
(A)
Explanation:
You're right in that
They're both nonpolar molecules, and
Note: Molecules with a greater number of polarizable electrons will have a greater degree of LDFs, because more electrons will both increase the chance of forming an instantaneous dipole and increase the polarity of that instantaneous dipole.
But we can't forget about our other choices:
(Everything in this question is nonpolar, so we can safely base our judgments of intermolecular forces on the number of polarizable electrons):
#Br_2# , which has#35 xx 2 = 70# polarizable electrons.#Cl_2# , which has#17 xx 2 = 34# polarizable electrons.- And
#F_2# , which has#9xx2=18# polarizable electrons.
In the end, we find that
That's why it has the greatest degree of intermolecular forces.
