Main Group Elements: Boiling & Melting Points - Video Tutorials & Practice Problems

Boiling Point and Melting Point

Here, we're going to say that boiling point and melting point abbreviated BP and MP respectively are the energy used to change an element from a liquid to gas. When we're talking about boiling point and from a solid to a liquid when we're talking about melting point. Now, here we're gonna have two overall trends that we're looking at and that's periodic periodic trend. One and periodic trend. Two to follow these trends, we're going to split our periodic table into two. In the first part, we're paying attention to groups one A to four A. Again, we're only concerned with our main group elements. So we're not gonna pay attention to our transition metals here, we're going to say going from group one A to four A, the boiling point and melting point tend to increase, moving from the, from left to right across the period and going up a group. So as we're heading towards this carbon, this is the overall trend, we'd expect our melting point to increase and our boiling point to increase. Now, let's look at the numbers here, we have lithium, its boiling point is 1347 and that's in degrees Celsius its melting point is 100 and 80 °C. Now, here, if we're looking, we can see that we're going from 6 71 6 88 7 66 8 81 to 1347. We can see the general trend as we're going up this group as it's increasing and this is a general trend that we typically see also in groups one A and four A. Now notice melting point as we're going up, we can see those are generally increasing as well. If you are pretty observant, you'll see that. Hey, why didn't you list any boiling point and melting points for group two A? Well, that's because in within that group because of numerous reasons. And again, we don't need to go delve into them directly. We're gonna have huge discrepancies. There's not gonna be an overall trade. That's easy to see. We're gonna see that it can increase as we go up and then decrease and then go back up. Again, the pattern is not uniform. So we just take away our boiling point and melting points from this group. Now, here, as we go to three A, we see the overall trend, we'd also see that in these last four here, they don't have any melting points present because again, there are exceptions here that are arising because of differences in bonding type as we're going from metallic to covina network bonding as atomic size is changing. So there's a lot of reasons why there isn't a uniform pattern for melting point for these four. So we just ignore those as well. That's why the overall trend when we pay attention to everything else is increasing. Now, if we look to group five A to eight A, there's something you'll also notice. Typically we see hydrogen here in group one A but hydrogen can also exist or act as a halogen. It's one electron away from being uh just like helium. It has similar bonding characteristics of the halogens. When it comes to melting point and boiling point, we can put it as part of group seven A because its overall pattern in terms of boiling point and melting point matches up, we're gonna say periodic trend, two, going from 58 to 8, a boiling point and melting point tend to decrease, moving from left to right across a period and going up a group here, we have exceptions with these here. Their pattern is all over the place. So we don't worry about the overall trend for them. But once we take a look at all the other elements, we can see that the overall trend is as we go up a group, we're going to have a decrease in boiling point and melting point. And as we go from flooring to hydrogen, you see that that continues, we see that this overall decrease in boiling point and melting point. So that's why we're allowed to place hydrogen here right. So from these two images, there's a lot that's being shown to us. But just remember from groups one A to four A, our boiling point and melting point overall is increasing as we go up a group to the right. From group 588 A, our overall trend for boiling point and melting point is that they decrease as we head towards the top, right. So keep that in mind when asked to compare or observe the differences in boiling point and melting point for our main group elements.

Main Group Elements: Boiling & Melting Points Example

Under standard conditions, which element will be most easily vaporized. Now, when we say most easily vaporized, that means which one becomes a gas most easily and between boiling point and melting point, this means we're talking about boiling point because that's where we go from a liquid to a gas. The one that's most easily changed into a gas would be the one with the lowest boiling point. Now, if we take a look at our options here, we have carbon, silicone, potassium rubidium and cesium. If you look at your periodic table, remember that carbon and silicone both can do covalent network bonding, this results in higher than normal boiling points and melting points. So those would not be our answers. If we look at potassium or bidi and SUSI looking on the periodic table, you'll see that they're all in group one A. So we have um potassium rubidium and SUSI. And remember for groups one A to four A as we go up and to the right of the periodic table, our boiling point increases here, we're looking for the lowest boiling point. So that means we the, the one lowest down which would be cesium So here our final answer would be option E.

Which of the following Group 5A elements would be expected to have the highest melting point?

• A. Nitrogen, N
• B. Phosphorus, P
• C. Oxygen, O
• D. Antimony, Sb
• E. Bismuth, Bi