Boron Family Reactions - Online Tutor, Practice Problems & Exam Prep

The group 3A elements, known as the Boron family, exhibit diverse reactivity due to their three valence electrons. Unlike groups 1A and 2A, these metals react with steam rather than liquid water, producing hydroxide ions and hydrogen gas. Thallium, with a preferred +1 oxidation state, behaves differently. When reacting with halogens, these metals form ionic halide solids, with the general formula M₃X₃ for group 3A metals and TlX for thallium. Understanding these reactions is crucial for grasping the properties and behaviors of these elements.

Boron Family Reactions

In this video, we're going to take a look at the elements in Group 3A, otherwise known as the Boron family elements. Now here we're going to say the reactions are driven by the presence of three valence electrons in their S&P subshells, and the two reactions that we're going to cover have to do with these Group 3 elements or boron family elements reacting with either water or a halogen.

If we take a look here, we already talked about groups 1A and 2A at this point and now we're moving on to Group 3A. In Group 3A we are met with some great diversity in terms of the elements because not all the elements are the same. Boron itself represents a metalloid, then we have a series of metals below it and then we have in Group 7-8, remember our radioactive row, which we don't really pay attention to because they're too unpredictable.

Within this, we also have different types of bonding that are possible. Remember we have metallic bonding and we have covalent network bondings that are possible. All these are going to play a role in how these elements react with either water or a halogen. So pay close attention and see the different types of reactions that are possible.

Reaction with H2O

Now the group through a elements are not as reactive with water like group 1A and 2A. In fact, we're going to say that the boron family metals do not react with water, but they do react with steam. So water has to be in a more volatile energetic state for the metals to pay any attention to that to it.

So if we take a look, we're going to say that we have our group 3A medals represented by M here, with thallium being outside of it. Remember here group 7-8 we don't even worry about this because it's radioactive. Now why is thallium different from the others? Well, we know that thallium is a group 3A and the predominant charge tends to be +3, but not when it comes to thallium. Thallium actually prefers having a plus one charge or plus one oxidation state. This makes it react differently as well as other things that are outside the scope of this course that cause it to react differently than the other group 3A metals.

Now for the group 3A medals, they react with gaseous water or steam. They're going to produce the ion form of themselves. They're in Group 3, so they're three plus we're going to produce hydroxide ion and H₂ gas. Balancing this out, we'd have a 2 here, a six here, A2 here, a six year, and a three here. Again, balancing is not what's important here. What's important is that these elements in Group three are less reactive with water, so you need to have it in in steam form. And then what's important is the charge of the majority of the group, 38 elements being plus three as a product and us producing hydroxide ion and gaseous hydrogen gas.

Now thallium reacts with water but a little bit differently. Remember thallium, it's predominant charges plus one. It would also produce hydroxide ion in H₂ gas. Balancing this out, we'd get 22, 2, two and one. So these will represent our different types of balanced reaction when different metals from group 3A react with steam.

Boron Family Reactions Example

Here it says complete and balance the following reaction. Here we have gallium liquid reacting with steam. Now gallium has a very low melting point. If you were to take solid gallium and put it in your hand, it would actually melt in your hand. That's how low its melting point is. So it's typical for us to find it in its liquid form.

Nevertheless, it's a group 3A metal and we know how it's going to react with water. Based on the example we've seen earlier, we know that it would produce the ionic form of gallium, which is gallium Ga3+ aq. We know that we produce also hydroxide ion and we form hydrogen gas.

We also know that our balance would be 2:6:2:6:3. Again, we're not really focusing on the balancing aspect. What's most important is that you know that gallium of Group 3A metal react with water would create the Ga3+ ion form of that metal plus hydroxide ion and hydrogen gas as products. So that's what's most important here.

Reaction with Halogens

When it comes to the reaction with halogens, we're going to say the Bourne family metals react with halogens to produce ionic halid solids. Now if we took a look here, we have in Group 3A all our metals and then thalium is different. So it's separate. They are plus 3IN charge. And remember halogens on group 7/8, so they're -1 in charge. This helps us to predict the product that will form.

The three would come here and the one would come here. Our product will be M3. We'd have to balance this out. We'd put a 2 here to give us 6 halogens on the product side. So we'd have to put a three here and A2 here. Thalium. Remember thallium is different. It's preferred oxidation state is not +3 but plus one, and then the halogens are still -1. The numbers in the charges are the same, so they just combine together to give us TLX.

Now here we'd have to balance this out. We have two halogens on the reactant side, but only one here. So we put a 2 here, which means I'd have to put a 2 here with thallium and then we could put A1 here for the diatomic halogen. This would represent our different reactions when these boron family metals react with our diatomic halogens. In all the reactions, we're going to produce an Ionic Halid solid.

Boron Family Reactions Example

Provide the products from the reaction between aluminum and chlorine. So when this reaction we have aluminum solid reacting with gaseous chlorine, remember that aluminums in Group 3/8, so it's three plus in its charge. Chlorine is a Group 7/8, so it's -1.

The numbers in the charges are different and when that happens, they don't just cancel out, we're going to crisscross them. The three comes here and the one comes here that'll give me aluminum chloride as a product. We still need to balance this reaction. We have two chlorines here, but three chlorines here.

The lowest common multiple is 6, so I'll put a three here and A₂ here. Now we have 2 aluminums on the product side, but only one on the reactant side, so I'd have to put a 2 here. So this represents my balanced chemical reaction between aluminum and chlorine.

Here’s what students ask on this topic:

What are the common reactions of Group 3A elements with water?

Group 3A elements, also known as the Boron family, do not react with liquid water but do react with steam. When these metals react with steam, they produce metal ions with a +3 charge, hydroxide ions, and hydrogen gas. The general reaction can be represented as:

$M\left(s\right)+3H{2}_O\left(g\right)\to M{3+}^{}\left(\mathrm{aq}\right)+3{\mathrm{OH}}_{-}\left(\mathrm{aq}\right)+3H{2}_g$

Thallium, however, reacts differently due to its preference for a +1 oxidation state, producing hydroxide ions and hydrogen gas with a different stoichiometry.

How do Group 3A elements react with halogens?

Group 3A elements react with halogens to form ionic halide solids. The general formula for these reactions is MX₃, where M represents the metal and X represents the halogen. The reaction can be represented as:

$M\left(s\right)+3X\left(g\right)\to M{X}_3\left(s\right)$

Thallium, due to its +1 oxidation state, forms a different product, TLX, with halogens. The reaction for thallium can be represented as:

$\mathrm{TL}\left(s\right)+X\left(g\right)\to \mathrm{TL}X\left(s\right)$

Why does thallium react differently from other Group 3A elements?

Thallium reacts differently from other Group 3A elements because it prefers a +1 oxidation state rather than the +3 oxidation state typical of other Group 3A metals. This difference in oxidation state affects its reactivity and the products formed during reactions. For example, when reacting with water, thallium produces hydroxide ions and hydrogen gas with a different stoichiometry compared to other Group 3A metals. Similarly, when reacting with halogens, thallium forms TLX instead of the typical MX₃ formed by other Group 3A metals.

What is the general formula for the products formed when Group 3A elements react with halogens?

The general formula for the products formed when Group 3A elements react with halogens is MX₃, where M represents the metal and X represents the halogen. This formula indicates that the metal forms a +3 ion and the halogen forms a -1 ion, resulting in the formation of an ionic halide solid. For example, if aluminum (Al) reacts with chlorine (Cl₂), the product would be AlCl₃.

What are the products of the reaction between thallium and steam?

When thallium reacts with steam, it produces thallium ions with a +1 charge, hydroxide ions, and hydrogen gas. The reaction can be represented as:

$\mathrm{TL}\left(s\right)+2H{2}_O\left(g\right)\to \mathrm{TL}{+}^{}\left(\mathrm{aq}\right)+2{\mathrm{OH}}_{-}\left(\mathrm{aq}\right)+H{2}_g$

This reaction differs from other Group 3A metals, which typically form +3 ions when reacting with steam.