[nickthegolfer]

Hey there.  We're breaking into a new chapter in my Chem course, and I really don't get it.  I'm struggling to grasp the concepts, but I need to finish this problem ASAP.  I figure if someone could explain these concepts, I'll be able to use that as a starting point for the rest of the chapter.  Anyways, here's the problem:

1. Use the principles of bonding and molecular structure to explain the following statements. 

a.) The boiling point of argon is -186 oC, whereas the boiling point of neon is -246 oC.

b.) Solid sodium melts at 98 oC, but solid potassium melts at 64 oC.

c.) more energy is required to break up a CaO(s) crystal into ions that to break up a KF(s) crystal into ions.

d.) Molten KF conducts electricity, but solid KF does not.

Thanks

[nickthegolfer]

I'd like to point out:  I am NOT asking for the answers, just if someone could give me a sort of explanation of the rules of chemical bonding, I'd be most grateful

[vhpk]

For b and c, you should explaination by using:
Separation Energy (E) ~ ( ionic eletric charge)/(distance of ions)
b/ the radial of K⁺ is bigger than Na⁺ so the energy is less -> the melting temperature is less
c/Similar to (b)
d/When KF molten, the moleculars will  separate into ions, these ions will mote with direction, so it can conduct electricity, but when it is solid, the molecular has a electrostatic suction force between ions, so ions can't mote freely, so it can't product electricity