0:02 so we were mostly uh concerned with
0:06 calent bonding in the previous example
0:08 uh and now we are going to be concerned
0:12 about ionic bond strengths and remember
0:14 ionic bonds is when we have a positive
0:17 and negative charge uh together and
0:20 those have an attractive forces so our
0:23 ionic solids is about this this ionic
0:25 kind of interaction the positive and
0:28 negative charges that are balancing each
0:32 other to cause the compound to become um
0:36 to to exist uh particularly in a solid
0:37 so the first thing we want to think
0:40 about is a lattice energy so our
0:43 definition of lattice energy is looking
0:47 at the reaction of some sort of ionic
0:51 solid and it's going to form its ions in
0:54 the gaseous state so it might form some
0:57 sort of charge on there and we have to
1:00 make sure it's about the gaseous state
1:03 and then we form the negative anion so
1:05 it's going to be some sort of negative
1:08 charge in there as a gaseous thing and
1:11 this is our Delta h of our
1:15 lattice so our Delta h of the
1:19 lattice is also due to this ionic
1:21 interaction so there's a lot of these
1:24 ionic interactions there's a constant in
1:27 here so it's the charge of the positive
1:31 ions times the charge of the negative
1:35 ions divided by the distance between
1:38 those positive and negative
1:42 charges and we call that R notot so for
1:45 example if we look at something like zinc
1:46 zinc
1:49 oxide versus something like sodium
1:52 chloride so zinc oxide is what we have
1:54 in sunscreen and we know when we go
1:57 swimming with sunscreen um the sunscreen
1:59 doesn't dissolve away so zinc oxide
2:03 doesn't dissolve um but why is that but
2:06 we if we take salt salt does dissolve
2:08 but if we just simply look at the
2:10 charges zinc is a plus two charge in
2:13 this compound oxygen is a minus
2:17 two our sodium is a plus one and the
2:21 chloride is a minus one so we have here
2:24 um lots of positive and negative charges
2:27 in zinc oxide so our Delta h of the
2:30 lattice of zinc oxide is going to be
2:35 greater than the Delta h of the lattice
2:39 of sodium chloride and because this
2:42 Delta H is actually very large it
2:44 doesn't dissolve so it's harder to break
2:48 up those ionic interactions when there's
2:51 this huge enthalpy of of lattice Energies
