Skip to main content
Pearson+ LogoPearson+ Logo
Start typing, then use the up and down arrows to select an option from the list.

General Chemistry

Learn the toughest concepts covered in Chemistry with step-by-step video tutorials and practice problems by world-class tutors

23. Chemistry of the Nonmetals

Periodic Trends and Diagonal Relationships

Diagonal Relationships are a way of linking similar chemical properties between elements in different groups. 

Diagonal Relationships

By looking at the periodic table diagonally we can form sets of elements with similar chemical properties. 


Diagonal Relationships of the Periodic Table

Play a video:
Was this helpful?
Hey, guys, In this new video, we're gonna take a look at periodic trends off certain elements in the periodic table. So we're gonna say, here we have what are called diagonal relationships. So diagonal relationships are similarities that exist between a period two elements, Remember, period to means road to and another element that is diagonally lower one level and to the right. So what do I mean by that? Lithium Zinn wrote to so down one level into the right. It has a relationship with magnesium. Beryllium is here, down one level, into the right. It acts like aluminum and then bore on here down one level and to the right, it acts like silicon. So when I say acts like, I mean, they're similar in terms of how they react with certain elements and compounds. So, for example, let's take a look at, um, lithium and magnesium first. So we're gonna say both of these react with elemental nitrogen, so end to to form nitrites. So remember, nitride is the charged form of nitrogen. It's in group five. So it has a minus three charge. Lithium is in group one A. So it's plus one. The numbers are different. So the one comes here, The three comes here. So this gives us Ally three n. I need to nitrogen. So I put it to here. But then that gives me six lithium. So I put a six year here. Magnesium is in group two ways, so it's plus two nitrogen again is minus three. So the two from here moves here. The three from here moves here. So we get em. G three and two. We have to nitrogen on both sides. So we're good. So we put a three here. Now both of these form hydraulic sides and carbonates that undergo thermal decomposition. Okay, so here, for example, if we talked about lithium, lithium could react with water, toe form, lithium hydroxide plus H two gas, which we don't care about. This could then react further and we'd get ally to co three. And if we did thermal decomposition, we add some heat. The heat would form our metal oxide plus carbon dioxide gas. Okay, so similar thing would happen with the magnesium. Now here, beryllium and aluminum, they're the next diagonal relationship. We look at both form oxide coatings that prevent reaction with water. Okay, so they don't behave like the other elements within their groups, reacting with water to reduce hydrogen. Instead, they make a metal coat so they don't go that far. In terms of reactions. Here, both form oxides that are not basic. Like the other metals in their groups, they form oxides that are AMFA Terek. So recall that the word AMFA Terek means something that behaves both as an acid or a base behaves as either and acid or a base now boron in silicon or the last diagonal relationship that we look at. So here, electrical electrically, they behave as semiconductors or semiconductors. So remember, metals conduct electricity so electricity can travel on their metal surface, whereas non metals are insulated, so they don't do that. Now we're gonna say here that metal Lloyds are a little bit of metals and non metals, so they act like conductors were not completely. They act like insulators, but not completely so we put them in the middle. So they're semiconductors now in their oxide or oxo acid forms. They represent week assets. Now, what exactly is an ox? Your Oxo acid. So recall in the section when we talk about naming acids and bases. Acids exist in two forms. We have our binary acids. Remember binary assets When you have an H plus plus a nonmetal in this type of acid, we have no oxygen, no medal. So here a good example HCL or HBR. So these are binary acids, oxy acids. On the other hand, this is when you have hpe plus connected to ah Polly Atomic ion with oxygen involved. So it's basically hpe plus connected to a non metal that is connected to oxygen's. So if we take a look here, we see that we have ah hydrogen. Here we have a non metal or metal Lloyd boron with oxygen's hydrogen here, non metal or metal Lloyd with oxygen. Same thing here. So all of these represent Oxy or Oxo acids. So the first one will be boric acid. Then we have metal. So Cilic Cilic acid, Then we have Selic acid, little funky. With the names here, these would all be weak acids here. Finally, they can combine with a hydride ion and represent a co violent hydride. Now here we have boring bh three and we have silent now for those of you are gonna go into organic chemistry. It's important to realize that you're going to see these molecules again when you get there. They are incredibly strong reducing agents. So basically they get oxidized, and in the process of them being oxidized, they reduce something else. And inorganic cam. When we say reduction, we're talking about actually donating hydrogen and electrons, so don't worry too much about that for right now. Just realize that here in their co violent hydride forms their strong reducing agents, they would also be very flammable as a byproduct. And then they would also have low melting points. So just realize that there's a lot of periodic turns we've talked about in the past, such as Ionic size, atomic radius, ionization, energy, electron affinity, effective nuclear charge. Here we there exists diagonal relationships, elements that are in different groups. But because of the arrangements of the periodic table, they're chemically similar, So these three cents just commit them to memory. Diagonal relationships move down one row, move over to the right, and that's how you connect the sets together. So just remember how they're grouped and what's special about each case