Electronic Configuration and Periodic Trends of Group 13 Elements
The Group 13 elements play a unique role in JEE Main Chemistry as they introduce key trends among the p-block elements. Also called the Boron group, these elements—boron (B), aluminium (Al), gallium (Ga), indium (In), and thallium (Tl)—occupy the 13th column in the modern periodic table. Each of these elements features three valence electrons and demonstrates an interesting transition from metalloid to metallic character down the group. Understanding the periodic trends, chemical properties, and real-world uses of Group 13 elements is essential for mastering both theoretical concepts and application-based questions in JEE.
Group 13 Elements: Definition, Members, and Periodic Table Position
Group 13 elements, known for having an outer electronic configuration of ns2np1, begin with boron and span down to thallium. Situated immediately after Group 12 in the p-block, their group number is 13 in modern IUPAC notation (or group IIIA in older systems).
- Boron (B) – atomic number 5
- Aluminium (Al) – atomic number 13
- Gallium (Ga) – atomic number 31
- Indium (In) – atomic number 49
- Thallium (Tl) – atomic number 81
A sixth element, nihonium (Nh), is sometimes included for completion, but its chemistry is not examined in JEE Main. Boron is a metalloid, while the remaining members are classified as metals.
Nomenclature: Why Are Group 13 Elements Called Icosagens or Triels?
Group 13 elements are commonly called the Boron group due to the unique and anomalous behavior of boron. The alternative name “Icosagens” is derived from the Greek “eikosi” (meaning 20) referencing their placement as Group 13: ‘20’ in the old group number system. The term “Triels” refers to the presence of three electrons in the outermost shell (trivalent nature).
| Name/Term | Origin/Meaning |
|---|---|
| Boron Group | After the first member, boron |
| Icosagens | ‘Eikosi’ = 20 in Greek (Group IIIA/13) |
| Triel | Trivalent (three valence electrons) |
You may also see references to the “Boron family” or “Aluminium group”, especially in older textbooks or competitive question banks.
Electronic Configuration of Group 13 Elements
The general electronic configuration for Group 13 elements is ns2 np1. This pattern explains their tendency to form +3 oxidation states and provides a foundation for understanding the periodic trends and chemistry across the group.
| Element | Symbol | Electronic Configuration |
|---|---|---|
| Boron | B | 1s2 2s2 2p1 |
| Aluminium | Al | [Ne] 3s2 3p1 |
| Gallium | Ga | [Ar] 3d10 4s2 4p1 |
| Indium | In | [Kr] 4d10 5s2 5p1 |
| Thallium | Tl | [Xe] 4f14 5d10 6s2 6p1 |
Notice the progressive filling of d and f orbitals in the heavier elements, which affects their atomic size, shielding, and chemical reactivity.
Physical and Chemical Properties of Group 13 Elements
To prepare efficiently for JEE, focus on trends such as metallic character, atomic radius, ionization energies, and nature of oxides. Compare these properties against other p-block elements like Group 14 and 15 for deeper insight.
| Property | Boron (B) | Aluminium (Al) | Gallium (Ga) | Indium (In) | Thallium (Tl) |
|---|---|---|---|---|---|
| Physical State | Solid (Brittle) | Metal | Metal | Metal | Metal |
| Nature | Metalloid | Metal | Metal | Metal | Metal |
| Oxidation State | +3 | +3 | +3 | +3, +1 | +3, +1 (more stable) |
| Amphoteric/Oxide Nature | Acidic | Amphoteric | Amphoteric | Amphoteric | Basic |
| Ionization Energy | Highest in group | Lower | Lower | Lower | Lowest in group |
| Other Features | Non-conductor, forms covalent bonds | Good conductor, amphoteric oxide | Low melting, forms GaAs semiconductor | Soft, forms alloys | Toxic, inert pair effect pronounced |
Key features: Only boron is a poor electrical conductor and non-metallic; others are malleable metals with increasing basic nature and metallic character as Z increases.
Trends and Reactivity Patterns Across the Boron Group
Several important periodic property trends are visible in Group 13. As you move from boron down to thallium, metallic character, atomic size, and basicity increase, while ionization enthalpy decreases (though not perfectly regularly, due to poor shielding from d and f electrons in Ga, In, Tl). The tendency for the +1 oxidation state also increases because of the inert pair effect.
- Ionization energy: Generally decreases, but higher for Ga due to d-block contraction.
- Oxidation states: +3 stable for B, Al, Ga; +1 becomes dominant for Tl (due to 6s2 inert pair).
- Electronegativity: Decreases from B (highest) to Tl (lowest).
- Reactivity: Boron is less reactive (due to high IE), Al is amphoteric and very reactive; Ga, In, Tl reactivity increases down the group.
Group 13 chemistry is also shaped by the anomalous behavior of boron (complex covalent compounds) versus typical metallic behavior and high lattice energies in aluminium.
Applications and Important Uses of Group 13 Elements
Group 13 elements are key to modern materials science and industrial applications, which are often tested in JEE Miscellaneous or Assertion-Reason questions.
- Boron is used in Borax, glass-making, detergents, and as a neutron absorber in nuclear reactors.
- Aluminium is crucial for aircraft alloys, packaging, foils, and as a reducing agent in metallurgy.
- Gallium is critical for semiconductors (GaAs), LEDs, and solar cells.
- Indium is used in LCD screens and plating alloys.
- Thallium has limited uses due to toxicity, mainly in electronic devices and some glass compositions.
For more on aluminium’s extraction, visit Metallurgy of Aluminium. For a full comparison with similar p-block groups, check p-block elements.
Mnemonic and Memory Tips for Group 13 Elements
Remembering the correct order of Group 13 elements is vital in MCQs. A popular mnemonic is: “Baba Ali Gaya India Tour”—Boron, Aluminium, Gallium, Indium, Thallium. Or, use “Big Animals Get Injured Thrice”.
- B → Boron
- Al → Aluminium
- Ga → Gallium
- In → Indium
- Tl → Thallium
Associate each with their unique uses for faster recall during problem-solving: e.g., aluminium–foils, gallium–semiconductors.
Solved Example: Exam-Oriented Question on Group 13
Example: Why does thallium form +1 ions more easily than +3, while boron and aluminium readily form +3?
Solution: The inert pair effect increases down the group. In thallium (Tl), the 6s2 electrons are less likely to participate in bonding due to poor shielding by filled 4f and 5d orbitals. As a result, Tl+ (+1) is more stable than Tl3+. For boron and aluminium, no inert pair effect operates, making +3 the stable oxidation state for both.
Carefully review Boron family reactions and group trend notes before the exam. Dive deeper into periodic property changes at classification of elements and periodicity for structured practice. For students seeking comprehensive JEE Main Chemistry resources, Vedantu provides exam-aligned notes, practice sets, and essential periodic trends theory explained by experienced faculty.
FAQs on Group 13 Elements: Explained for Exams and Quick Revision
1. How to remember group 13 elements?
Group 13 elements can be remembered using a simple mnemonic to help you recall their order easily for exams.
Mnemonic Example: ‘Be A Good Indian Teenager’ for Boron (B), Aluminium (Al), Gallium (Ga), Indium (In), and Thallium (Tl).
Memory Tips:
- Start each word with the element’s symbol.
- Write and repeat the list several times.
- Use flashcards or quizzes before exams for quick revision.
2. Why are group 13 elements called icosagens?
Group 13 elements are called icosagens because the Greek prefix ‘icosa-’ means 20, relating to their position as group 13 (older numbering: group IIIA, or group 13 among 18 groups — 13th main group).
Other Names:
- Boron group
- Triel family
- Icosagens
3. What makes group 13 elements unique?
Group 13 elements are unique due to their combination of metallic and non-metallic properties and variable oxidation states.
Key Features:
- Boron is a metalloid, while others are metals.
- Common oxidation state is +3, but heavier elements also show +1 (due to inert pair effect).
- They exhibit a diagonal relationship and distinctive periodic property trends.
4. Are group 13 elements metals or nonmetals?
Group 13 elements show both metallic and non-metallic behavior.
Classification:
- Boron: Metalloids (shows both metal and nonmetal characteristics)
- Aluminium, Gallium, Indium, Thallium: Metals
5. What are the main properties of group 13 elements?
Group 13 elements share certain physical and chemical properties.
Key Properties:
- Electronic configuration: ns2np1
- Oxidation states: Mainly +3; +1 for heavier elements (Indium, Thallium)
- Atomic & Ionic radii: Increase down the group
- Ionization enthalpy: Relatively high, decreases down group except for instability due to d/f-block contractions (for Ga)
- Boron is a metalloid; the rest are metals
6. Do group 13 elements gain or lose electrons during bonding?
Group 13 elements generally lose electrons during reactions, leading to a positive oxidation state (usually +3).
Oxidation Details:
- They lose three electrons from the outer shell: two from the s orbital and one from the p orbital (ns2np1 → n-1 shell).
- This forms M3+ cations, especially for Al, Ga, In.
7. What is the electronic configuration pattern in group 13?
Group 13 elements follow a common pattern in their valence shell electronic configuration.
General Pattern:
- Valence shell: ns2np1
- Example: Boron (1s22s22p1), Aluminium (1s22s22p63s23p1), and so on.
8. Why does boron, unlike aluminium, act as a metalloid while others are metals?
Boron acts as a metalloid due to its small atomic size, high ionization energy, and inability to conduct electricity like metals.
Main Reasons:
- Boron forms covalent compounds, is poor conductor, and does not exhibit metallic luster.
- Other group 13 elements have larger atoms and lower ionization energies, resulting in metallic character.
9. Why does the +1 oxidation state become more stable down the group (inert pair effect)?
The +1 oxidation state becomes increasingly stable in heavier group 13 elements due to the inert pair effect.
Explanation:
- Down the group, the s-electrons of the valence shell become less available for bonding due to poor shielding by inner d and f orbitals.
- This results in the s-electrons remaining paired — hence, +1 state is favored for thallium and indium.
10. What are the main uses of Group 13 elements?
Group 13 elements are important in many industrial and scientific fields.
Major Applications:
- Boron: Used in glass manufacturing, detergents, and as a neutron absorber in nuclear reactors.
- Aluminium: Key metal for construction, transport (aircraft), packaging, and electrical cables.
- Gallium: Essential in semiconductors and LEDs.
- Indium: Used in touch screens and specialized alloys.
- Thallium: Used in electronics and optical systems (though toxic).
