Group 13 Elements | Chemistry of Boron Family

The group 13 elements or group 3A are also called the boron family. The elements of group 13 of the periodic table consisting of boron, aluminum, gallium, indium, and thallium.

General Trend of Group 13 Elements

The general trend of group 13 elements are given below:

• The metallic character of group 3A increases down the group.
• P-orbital is in the process of filling.
• All the elements show a +3 oxidation state.
• All the elements give MX₃ halides.
• Boron is a non-metal but other elements are metal.
• The elements of group 13 give normal oxide.
• Ga, In, and Ti are rare elements.

Properties of Group 13 Elements

Boron

• Atomic number: 5
• Atomic symbol: B
• Atomic mass: 10.811
• Density: 2.34
• Melting point: 2300°C
• Boiling point: 2550°C
• Atomic radius: 87
• Covalent radius: 82
• Electronegativity: 2.04
• Electron affinity: 26.7 KJ/mol
• Magnetic type: Diamagnetic
• Electrical type: Insulator
• Year discovered: 1808

Aluminum

• Atomic number: 13
• Atomic symbol: Al
• Atomic mass: 26.98
• Density: 2.698
• Melting point: 660°C
• Boiling point: 2467°C
• Atomic radius: 118
• Covalent radius: 118
• Electronegativity: 1.61
• Electron affinity: 42.5 KJ/mol
• Magnetic type: Paramagnetic
• Electrical type: Conductor
• Year discovered: 1825

Gallium

• Atomic number: 31
• Atomic symbol: Ga
• Atomic mass: 69.723
• Density: 5.907
• Melting point: 30°C
• Boiling point: 2403°C
• Atomic radius: 136
• Covalent radius: 126
• Electronegativity: 1.81
• Electron affinity: 28.9 KJ/mol
• Magnetic type: Diamagnetic
• Electrical type: Conductor
• Year discovered: 1875

Indium

• Atomic number: 49
• Atomic symbol: In
• Atomic mass: 114.8
• Density: 7.31
• Melting point: 157°C
• Boiling point: 2000°C
• Atomic radius: 156
• Covalent radius: 144
• Electronegativity: 1.78
• Electron affinity: 28.9 KJ/mol
• Magnetic type: Diamagnetic
• Electrical type: Conductor
• Year discovered: 1863

Thallium

• Atomic number: 81
• Atomic symbol: Ti
• Atomic mass: 204.38
• Density: 11.85
• Melting point: 303°C
• Boiling point: 1457°C
• Atomic radius: 156
• Covalent radius: 148
• Electronegativity: 1.62
• Electron affinity: 19.2 KJ/mol
• Magnetic type: Diamagnetic
• Electrical type: Conductor
• Year discovered: 1861

Boron | Overview, Properties, Uses

Peculiar Behavior of Boron

Boron	Other Group 13 Elements
Boron is a metal.	Other elements are non-metal.
Boron show +3, -3 oxidation state.	Al, Ga, In, and Ti show only a +3 oxidation state.
Boron does not form ionic compounds.	Other elements form ionic compounds.
Forms acidic oxide.	Amphoteric oxide except thallium.
It can form acids like H3BO3, HBO2, etc.	Do not form acids.
It forms molecular addition compounds.	Do not form molecular addition compounds.

What is Inert Pair Effect In Group 13 Elements?

B₅ = [He]₂, 2s², 2p¹

Al₁₃ = [Ne]₁₀, 3s², 3p¹

Ga₃₁ = [Ar]₁₈, 3d¹⁰, 4s², 4p¹

In₄₉ = [Kr]₃₆, 4d¹⁰, 5s², 5p¹

Ti₈₁ = [Xe]₅₄, 4f¹⁴, 5d¹⁰, 6s², 6p¹

First of all, to know the reason for the inert pair effect, we will know the term shielding effect.

The valence electron of aluminum is attracted by the nucleus but the valence electron of aluminum show repulsion toward the inert electron of Al. So, the valence electron of the aluminum shows both attraction (towards the nucleus) and repulsion (toward the inert electron). The repulsion force of the inert electron of an atom towards the valence electron is called the shielding effect. The order of shielding effect is:

s > p > d > f

Does Gallium Show Inert Pair Effect?

In the case of Gallium, 3d10 is present and 10 electrons in the 3d subshell which is poorly shielded toward 4s² and 4p¹ subshell electrons. It means that 3d¹⁰ subshell electrons poorly Shield the 4s² and 4p¹ electrons.

So due to the poor shielding effect, 4s2 subshell electrons are attracted toward the nucleus strongly. That’s why 4s² not easily loses electrons and does not take part in bond formation and gallium easily loses one electron of 4p1 and forms Ga1+, but if three electrons are removed and form Ga3+, more and more energy is required to form Ga3+. So, the inertness of 4s2 subshell electrons is called the inert pair effect.

Does Indium Show Inert Pair Effect?

In the case of Indium, 4d10 subshell electrons are present and before 4d¹⁰, 3d¹⁰ is also present. The electrons of 3d and 4d subshell poorly shield toward 5s² and 5p¹ subshell electrons. Due to the poor shielding effect of 3d10 and 4d10 on 5s2 and 5p1, the 5s2 attracted toward the nucleus strongly. That’s why 5s2 does not easily lose electrons and does not take part in bond formation. That’s why indium easily forms In1+ but not In3+. So, the inertness of 5s2 subshell electrons is called the inert pair effect.

Does Thallium Show Inert Pair Effect?

In the case of Thallium, 4f¹⁴ and 5d¹⁰ subshell electrons are present, and as we know the f-subshell has a very poor shielding effect toward the valance electrons. The electrons of 4f and 5d are very poorly shielded by the 6s2 and 6p1 electrons, and 6s2 show a stronger force of attraction toward the nucleus. That’s why thallium 6s2 valance electrons do not take part in bond formation. Thallium easily forms a +1 oxidation state but not +3 and we can say that Ti1+ is more stable than Ti3+. So, the inertness of 6s2 subshell electrons is called the inert pair effect.

As we move from top to bottom in a group, the inert pair effect increase. The order of inert pair effect of group-13 is:

Ti > In > Ga

Chemical Properties of Group 13 Elements

Reactions of Boron

React with Acid

Boron reacts with strong oxidizing acids such as nitric acid or hot concentrated sulfuric acid to form boric acid.

B + 3HNO₃ → H₃BO₃ + 3NO₂

2B + 3H₂SO₄ → 2H₃BO₃ + 3SO₂

React with Alkalies

Boron reacts with boiling concentrated sodium hydroxide to form sodium metaborate and hydrogen gas is also evolved.

2B + 2NaOH + 2H₂O → 2NaBO₂ + 3H₂

React with Water

2B + 6H₂O → 2H₃BO₃ + 3H₂

React with Oxygen

Oxides are formed by the direct reaction of boron with oxygen.

2B + 3O₂ → B₂O₃

React with Sulfur

Boron directly reacts with sulfur at high temperatures and forms sulfides.

2B + 3S → B₂S₃

The boron sulfides are hydrolyzed by water.

B₂S₃ + 6H₂O → 2H₃BO₃ + 3H₂S

React with Nitrogen

Boron directly reacts with nitrogen and forms boron nitride.

2B + N₂ → 2BN

Reactions of Aluminium

React with Water

At room temperature, Aluminium does not react with H₂O but reacts with stream-evolving hydrogen gas.

2Al + 6H₂O → 2Al(OH)₃ + 3H₂

React with Hydrogen

Aluminum combine with hydrogen gas and forms aluminum hydride.

2Al + 3H₂ → 2AlH₃

React with Oxygen

Oxides of aluminum are formed by the reaction of aluminum with oxygen. Aluminum oxides are used in flashlight photography.

4Al + 3O₂ → 2Al₂O₃

React with Halides

Aluminum reacts with halogens X₂ and forms 2AlX₃. This reaction is exothermic in nature.

2Al + 3X₂ → 2AlX₃

2Al + 3Cl₂ → 2AlCl₃

React with Acids

2Al + 6HCl → 2AlCl₃ + 3H₂

2Al + 6H₂SO₄ → Al₂(SO₄)₃ + 3SO₂ + 6H₂O

Al + HNO₃ → NO Reaction

React with Alkali

It reacts with alkali and forms soluble sodium aluminate and liberates hydrogen gas.

2Al + 2NaOH + 6H₂O → 2NaAl(OH)₄ + 3H₂

2Al + 2NaOH + 2H₂O → 2NaAlO₂ + 3H₂

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