Group 13 Elements: The Boron Family (Properties, Notes)

We are all familiar with the periodic table. Isn’t it difficult to recall all of the properties of the elements? There are \(18\) groups and \(7\) periods in the periodic table for studying the properties of each element. You have probably heard of boron. Boron is used in the production of popular fibreglass. In this article, we will learn about the Group 13 Elements: The Boron Family, from the periodic table.

Introduction to Group 13 Elements

Group \(13\) represents the boron family and the elements having an \({\rm{n}}{{\rm{s}}^{\rm{2}}}{\rm{n}}{{\rm{p}}^{\rm{1}}}\) configuration. It includes boron \(\left( {\rm{B}} \right)\) aluminium \(\left( {{\rm{Al}}} \right)\), gallium \(\left( {{\rm{Ga}}} \right)\), Indium \(\left( {{\rm{In}}} \right)\) thallium \(\left( {{\rm{Tl}}} \right)\), and the newly discovered element, ununtrium \(\left( {{\rm{uut}}} \right)\) which is radioactive. Except for boron, which is non-metal, all of the elements in this group have metallic properties. The non-metallic character of B may be due to its small size, high ionization enthalpy, and relatively high electronegativity.

Occurrence of Boron

Boron is a relatively rare element that is well known due to its presence in borax deposits. Aluminium is the third most abundant element \(\left( {8.3\% } \right)\) in the earth’s crust after oxygen \(\left( {46.0\% } \right)\) and silicon \(\left( {27.7\% } \right).\) The remaining three elements (Ga, In and TI) are found in trace amounts as sulphides in zinc and lead sulphide ores.

The important minerals of boron are as follows:

1. Borax: \({\rm{N}}{{\rm{a}}_2}\left[ {\;{{\rm{B}}_4}{{\rm{O}}_5}{{({\rm{OH}})}_4}} \right] \cdot 8{{\rm{H}}_2}{\rm{O}}\)
2. Kernite: \({\rm{N}}{{\rm{a}}_2}\left[ {\;{{\rm{B}}_4}{{\rm{O}}_5}{{({\rm{OH}})}_4}} \right]\)
3. Colemanite: \({\rm{Ca}}\left[ {{{\rm{B}}_3}{{\rm{O}}_4}{{({\rm{OH}})}_3}} \right].{{\rm{H}}_2}{\rm{O}}\)
4. Orthoboric acid: \({{\rm{H}}_3}{\rm{B}}{{\rm{O}}_3}\)

The important minerals of aluminium are as follows:

1. Bauxite: \({\rm{A}}{{\rm{l}}_2}{{\rm{O}}_3} \cdot {\rm{x}}{{\rm{H}}_2}{\rm{O}}\)
2. Kaolinite: \({\rm{A}}{{\rm{l}}_2}{({\rm{OH}})_4} \cdot {\rm{S}}{{\rm{i}}_2}{{\rm{O}}_5}\)
3. Cryolite : \({\rm{N}}{{\rm{a}}_3}{\rm{Al}}{{\rm{F}}_6}\)

Electronic Configuration of Group 13 Elements

The general valence shell electronic configuration of group \(13\) elements is \({\rm{n}}{{\rm{s}}^{\rm{2}}}{\rm{n}}{{\rm{p}}^{\rm{1}}}{\rm{,}}\) where \(\mathrm{n}=2-7\) While boron and aluminium have noble gas cores, gallium and indium have noble gas plus \(10\) d-electrons, and thallium has noble gas plus \(14\,{\rm{f}}\)-plus \(10\,{\rm{d}}\)-electron cores. 

As a result, the electronic configurations of elements in group \(13\) are more complex than those in groups \(1\) and \(2.\) Thus the chemistry of all the elements in this group is affected by this difference in electronic configurations. The table shows the whole electronic configuration of these elements.

Physical Properties of the Boron Family (Group 13 Elements)

The physical properties of the born family are explained below

1. Atomic and Ionic Radii:

The atomic and ionic radii of group \(13\) elements are smaller than those of group \(2\) elements. Both atomic and ionic radii are expected to increase as one moves down the group, owing to the addition of a new electron shell with each succeeding element. There are, however, some deviations as we move from \({\rm{Al}}\) to \({\rm{GA}}\) For example, the atomic radius of \({\rm{Ga (135\, pm)}}\) is slightly lower than that of \({\rm{Al(143\, pm)}}\)

2. Ionization Enthalpies:

The first ionization enthalpies \(\left( {{{\rm{\Delta }}_{\rm{i}}}{{\rm{H}}_{\rm{1}}}} \right)\) of group \(13\) elements are lower than those of group \(2\) elements, i.e. alkaline earth metals. Moving down in group \(13\) from B to Al results in a sharp decrease in first ionization enthalpy \(\left( {{{\rm{\Delta }}_{\rm{i}}}{{\rm{H}}_{\rm{1}}}} \right)\) of Al due to an increase in atomic size and screening effect (of the \({\rm{2s}}\) and \({\rm{2p}}\) electrons), which outweighs the effect of increased nuclear charge. However, the \(\left( {{{\rm{\Delta }}_{\rm{i}}}{{\rm{H}}_{\rm{1}}}} \right)\)  of Ga is only slightly higher \(\left( {{\rm{2\;kJ\;mo}}{{\rm{l}}^{{\rm{ – 1}}}}} \right)\) than that of Al, while that of Tl is much higher than those of Al,  Ga and In.

3. Electronegativity

The elements of the boron family (group \(13)\) are more electronegative than those of the alkali metals (group \(1)\) and alkaline earth metals (group \(2).\) Electronegativity decreases from B to Al and then increases marginally down the group.

4. Electropositive Character-Metallic Character

Group \(13\) elements are less electropositive or metallic than alkali metals (group \(1)\) and alkaline earth metals (group \(2).\) The electropositive character of the elements increases from boron to aluminium and then decreases from aluminium to thallium as one moves down the group.

5. Density

Elements in group \(13\) have higher densities than elements in group \(2\) due to smaller atomic and ionic radii. The densities increase as you move down the group. This is due to an increase in the atomic mass of elements, which outweighs the effect of increased atomic size. However, the densities of boron and aluminium are much lower than those of the other members.

6. Melting and Boiling Points

The melting points of group \(13\) elements do not follow a regular pattern, as elements from groups \(1\) and \(2\) do. This is most likely due to the peculiar crystal structures of B and Ga. Actually, as one moves down the group from B to Ga, the melting points decrease sharply and then increase from Ga to Tl. Thus, Ga has the lowest melting point \((303 \mathrm{~K})\) of the elements in group \(13\) and can exist as a liquid at room temperature in summer.

Chemical Properties of the Boron Family (Group 13 Elements)

1. Oxidation state: The elements of group \(13\) have two electrons in the s-orbital and one electron in the p-orbital. As a result, these elements should have a uniform oxidation state of \(+3.\) This is true for boron and aluminium, which have an oxidation state of \(+3,\) but gallium, indium, and thallium have oxidation states of both \(+1\) and \(+3\) due to the inert pair effect.

2. Reducing Nature: Because it has no tendency to lose valence electrons, the first element, boron, is not a reducing agent. A reducing agent is an aluminium. Since the released hydration energy offsets the ionization energy necessary to lose electrons in an aqueous solution. The reducing character, in general, decreases down the group in the order \(\mathrm{Al}>\mathrm{Ga}>\mathrm{In}>\mathrm{Tl}\)

3. Formation of Hydrides: The elements in group \(13\) (Boron Family) do not directly combine with hydrogen to form hydrides. However, a number of these elements’ hydrides have been prepared indirectly.

4. Formation of Halides: The elements of group \(13\) react with halogens at high temperatures, forming trihalides of the general formula, \(\mathrm{MX}_{3}\) Thallium (III) iodide \(\left( {{\rm{Tl}}{{\rm{l}}_{\rm{3}}}} \right)\) is, however, unknown.

\(2{\rm{M(s) + 3}}{{\rm{X}}_{\rm{2}}}{\rm{(g)}}\mathop  \to \limits^{{\rm{ Heat }}} 2{\rm{M}}{{\rm{X}}_3}({\rm{X}} = {\rm{F}},{\rm{Cl}},{\rm{Br}},{\rm{I}})\)

5. Formation of Oxides (Reactivity towards air): All the metals of group \(13\) react with dioxygen at high temperatures to form trioxides of the formula, \({{\rm{M}}_2}{{\rm{O}}_3}\)

6. Formation of Hydroxides: The hydroxide, \({\rm{M}}{({\rm{OH}})_3}\) are formed by dissolving the metal oxides, \({{\rm{M}}_2}{{\rm{O}}_3}\), in water.

\(\mathop {{{\rm{M}}_2}{{\rm{O}}_3}}\limits_{{\rm{Metal}}\,\,{\rm{oxide}}}  + 3{{\rm{H}}_2}{\rm{O}} \to \mathop {2{\rm{M}}{{({\rm{OH}})}_3}}\limits_{{\rm{Metal}}\,\,{\rm{hydroxide}}} \)

The behaviour of the hydroxides is similar to that of oxides, i.e., \({\rm{B}}{({\rm{OH}})_3}\) or boric acid is a typical acid, \({\rm{Al}}{({\rm{OH}})_3}\) and \({\rm{Ga}}{({\rm{OH}})_3}\) are both amphoteric while \(\ln {({\rm{OH}})_3}\) and \({\rm{Tl}}{({\rm{OH}})_3}\) are basic in nature.

7. Reactivity towards acids and alkalies: 

A. The action of acids: Boron does not react with non-oxidizing acids such as hydrochloric acid. However, high temperatures are caused by strong oxidizing acids, such as a mixture of hot conc. \({{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}\) and \({\rm{HN}}{{\rm{O}}_3}(2:1)\) forming boric acid \(\left( {{{\rm{H}}_3}{\rm{B}}{{\rm{O}}_3}} \right)\)

All other elements react with both oxidizing and non-oxidizing acids. For example, aluminium reacts with dilute hydrochloric acid and liberates hydrogen gas.

\({\rm{2Al(s) + 6HCl(aq)}} \to {\rm{2A}}{{\rm{l}}^{{\rm{3 + }}}}{\rm{(aq) + 6C}}{{\rm{l}}^{\rm{ – }}}{\rm{(aq) + 3}}{{\rm{H}}_{\rm{2}}}{\rm{(g)}}\)

B. The action of Alkalies: Boron is resistant to the action of alkalies \({\rm{(NaOH \;or\; KOH)}}\) up to \({\rm{773\, K}}\) but above this temperature, it reacts, forming borates and liberating dihydrogen gas.

Summary

Group \(13\) represents the boron family, and the elements have an \({\rm{n}}{{\rm{s}}^{\rm{2}}}{\rm{n}}{{\rm{p}}^{\rm{1}}}\) configuration. It includes boron \(\left( {\rm{B}} \right)\) aluminium \(\left( {{\rm{Al}}} \right)\) gallium \(\left( {{\rm{Ga}}} \right)\), Indium \(\left( {{\rm{In}}} \right)\) thallium \(\left( {{\rm{Tl}}} \right)\) and the newly discovered element, ununtrium \(\left( {{\rm{uut}}} \right)\) which is radioactive. The atomic and ionic radii of group \(13\) elements are smaller than those of group \(2\) elements. The elements of the boron family (group \(13)\) are more electronegative than those of group I and group II elements.

FAQs On Group 13 Elements

The most commonly asked questions about Group 13 elements are answered here:

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