Boron Family-Elements, Configurations, Periodic trend, Physical & Chemical Properties, FAQs

February 14, 2025December 23, 2024 by Neeraj Anand, Param Anand

About Boron Family

Boron got its name from the Arabic word ‘buraq’ which is the name of borax. It belongs to the 13th group of the p block element. The elements of the 13th group are boron, aluminium, gallium, indium, and thallium. They all are metallic in nature except boron which is a metalloid. All of them have 3 electrons in the outermost shell which has the electronic configuration of ns²np¹. There are two oxidation states (+3 and +1) of boron family.

Boron is a non-metal but the second element is aluminium which is a metal. Gallium, indium, and titanium are almost metallic in nature. Aluminium is also one of the most important members of the boron family which has an atomic number of 13 and chemical symbol is Al. It is very expensive to produce aluminium because for electrolysis of one mole of aluminium, we require 3 moles of electron and thus a huge amount of energy is used.

Electronic Configuration of Boron Family

The general electronic configuration of Boron family is ns²np¹

Element	Atomic Number	Electronic Configuration
Boron (B)	5	[He] 2s²2p¹
Aluminium (Al)	13	[Ne] 3s²3p¹
Gallium (Ga)	31	[Ar] 3d¹⁰4s²4p¹
Indium (In)	49	[Kr] 4d¹⁰5s²5p¹
Thallium (Tl)	81	[Xe] 4f¹⁴ 5d¹⁰6s²6p¹

Atomic and Ionic Radii of Boron Family

Element	Atomic Radius/pm	Ionic Radius(M³⁺)/pm
Boron (B)	85	27
Aluminium (Al)	143	53.5
Gallium (Ga)	135	62.0
Indium (In)	167	80.0
Thallium (Tl)	170	88.5

As we move from top to bottom in the periodic table the atomic and ionic radius increase because down the group number of new shells are added as a result the magnitude of screening effect increases which decreases the attraction between valence electrons and nucleus of the atom.

Note: Some anomalies observed:

There is a sharp increase in atomic and Ionic radius from Boron to Aluminium

In case of Al(2,8,3) there is a greater Screening effect by the 8 electrons present in the penultimate shell resulting in decreased effective nuclear charge. Therefore, the atomic radius is more than the expected value. However there is no such effect observed for B atom (2,3) since it has only two shells.

The atomic radius of Gallium is less than that of Aluminium.

In the Gallium the atomic radius decreases as compared to the Aluminum because of the presence of 3d elements. Since d-orbitals have less shielding effect, it increases the effective nuclear charge of Ga. However in such cases it is not observed in the case of ionic radius. It increases regularly.

Ionisation Enthalpy of Boron Family

Elements	Ionisation enthalpy(△H1)/kJ mol-1
Boron (B)	800
Aluminium (Al)	577
Gallium (Ga)	578
Indium (In)	558
Thallium (Tl)	590

The ionisation value from B to Al decreases sharply because of the bigger size of the Al atom. But the element Ga ten electrons present in the 3d subshell which do not screen as much as is done by s and p electrons, therefore, there is an unexpected increase in the magnitude of effective nuclear charge resulting in increased value. The same explanation can be offered in moving from In to Tl. The latter has fourteen 4f electrons with very poor shielding effect. This also results in an unexpected increase in the effective nuclear charge of Tl.

Oxidation State of Boron Family

The following trends are observed in the oxidation states of Boron Family

The first two elements Boron and Aluminium show +3 oxidation state.
The remaining elements Gallium, Indium and Thallium show both +1 and +3 oxidation states.
The stability of +3 oxidation state decreases from Aluminium onwards and the last element Thallium, +1 oxidation is more stable than +3.
So that TlCl is more stable than TlCl₃.

The above trend is explained with the help of the Inert pair effect.

Inert Pair Effect

As a result of the inert pair effect, the electron pair representing the valence s- electrons is more exposed to the nucleus than the p-electrons. In other words, these are held tightly by the nucleus and are not readily available for the bond formation. However, valence p-electrons are available for the same. The inert pair effect becomes more predominant as we go down the group as a result the valence p-electrons will be more available accounting for the +1 oxidation state. The inert pair effect is maximum in the last element thallium (Tl) in the boron family. Therefore TlCl is more stable than TlCl₃.

Chemical Properties of Boron Family

Formation of Hydrides: The elements present in group 13 do not combine directly with hydrogen to form hydrides. However, a number of hydrides of these have been prepared indirectly. Boron, the first member of the family, forms a number of hydrides called Boranes.
These are two types,

B_nH_n+4 : B₂H₆ ,B₃H₇, B₄H₈ etc.

B_nH_n+6 : B₄H₁₀, B₅H₁₁, B₆H₁₂ etc.

Out of the boranes, the most important is diborane is prepared following way:

By the reduction of boron trifluoride with LiAlH₄ in diethyl ether as

4BF₃ + 3LiAlH₄ → 2 B₂H₆ + 3LiF + 3AlF₃

To learn more about the chemical properties of Boron family you may visit the following link: Chemical Properties of The Borane Family

Do you know why aluminium does not react with water?

A protected layer of Al₂O₃ is formed due to which it does not react with water. This process is also called as anodising.

Gallium which has chemical formula Ga and atomic number 31 and has the second-lowest melting point after mercury and it can persist in a liquid phase at larger temperature than any other substance. Gallium is very important industrially as it forms Gallium arsenide which converts light directly into electricity.

Indium is also one of the p block element with atomic number 49. Indium is also soft malleable metal just like gallium. In the acids indium is soluble but at room temperature, it does not react with oxygen. Indium is used for increasing the strength of metals and is also used in making alloys.

Thallium which has chemical formula Tl is a heavy element and is also very stable in +1 oxidation state. Even though it’s poisonous then also it is used in high-temperature superconductors.

There is a diagonal relationship between beryllium and aluminium which is that when it reacts with water both of these compounds produce hydronium ions, and one more similarity between these two is that both of them are amphoteric in nature.

To learn more about P-block elements, register with ANAND CLASSES (A School Of Competitions) and download our app.

Frequently Asked Questions-FAQs

1. Why is Group 13 called the boron family?

Boron is the first element of the group-13 elements. So that group 13 is named as Boron Family. The remaining elements of the Boron family are Aluminium (Al), Gallium (Ga), Indium (In) and Thallium (Tl).

2. How does boron differ from other members of Group 13 elements?

Due to its smaller size and unavailability of d-electrons boron is found to exhibit properties which are in contrast to the other elements of the boron family. These properties are known as anomalous properties of boron. Some of these are the maximum covalency of boron is 4 due to the absence of d orbitals. The boron oxides and hydroxides are acidic in nature, whereas the other elements in the family form oxides and hydroxides which are amphoteric in nature.

3. Which element shows diagonal relationship with boron?

Boron and silicon are diagonally related with each other.

4. What is the reason for the inert pair effect?

The electron pair representing the valence s- electrons is more exposed to the nucleus than the p-electrons. In other words, these are held tightly by the nucleus and are not readily available for the bond formation. However, valence p-electrons are available for the same. This effect is called the inert pair effect.

Neeraj Anand, Param Anand

Er. Neeraj K.Anand is a freelance mentor and writer who specializes in Engineering & Science subjects. Neeraj Anand received a B.Tech degree in Electronics and Communication Engineering from N.I.T Warangal & M.Tech Post Graduation from IETE, New Delhi. He has over 30 years of teaching experience and serves as the Head of Department of ANAND CLASSES. He concentrated all his energy and experiences in academics and subsequently grew up as one of the best mentors in the country for students aspiring for success in competitive examinations. In parallel, he started a Technical Publication "ANAND TECHNICAL PUBLISHERS" in 2002 and Educational Newspaper "NATIONAL EDUCATION NEWS" in 2014 at Jalandhar. Now he is a Director of leading publication "ANAND TECHNICAL PUBLISHERS", "ANAND CLASSES" and "NATIONAL EDUCATION NEWS". He has published more than hundred books in the field of Physics, Mathematics, Computers and Information Technology. Besides this he has written many books to help students prepare for IIT-JEE and AIPMT entrance exams. He is an executive member of the IEEE (Institute of Electrical & Electronics Engineers. USA) and honorary member of many Indian scientific societies such as Institution of Electronics & Telecommunication Engineers, Aeronautical Society of India, Bioinformatics Institute of India, Institution of Engineers. He has got award from American Biographical Institute Board of International Research in the year 2005.

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CBSE Class 11 Chemistry Syllabus

CBSE Class 11 Chemistry Syllabus is a vast which needs a clear understanding of the concepts and topics. Knowing CBSE Class 11 Chemistry syllabus helps students to understand the course structure of Chemistry.

Unit-wise CBSE Class 11 Syllabus for Chemistry

Below is a list of detailed information on each unit for Class 11 Students.

UNIT I – Some Basic Concepts of Chemistry

General Introduction: Importance and scope of Chemistry.

Nature of matter, laws of chemical combination, Dalton’s atomic theory: concept of elements,
atoms and molecules.

Atomic and molecular masses, mole concept and molar mass, percentage composition, empirical and molecular formula, chemical reactions, stoichiometry and calculations based on stoichiometry.

UNIT II – Structure of Atom

Discovery of Electron, Proton and Neutron, atomic number, isotopes and isobars. Thomson’s model and its limitations. Rutherford’s model and its limitations, Bohr’s model and its limitations, concept of shells and subshells, dual nature of matter and light, de Broglie’s relationship, Heisenberg uncertainty principle, concept of orbitals, quantum numbers, shapes of s, p and d orbitals, rules for filling electrons in orbitals – Aufbau principle, Pauli’s exclusion principle and Hund’s rule, electronic configuration of atoms, stability of half-filled and completely filled orbitals.

UNIT III – Classification of Elements and Periodicity in Properties

Significance of classification, brief history of the development of periodic table, modern periodic law and the present form of periodic table, periodic trends in properties of elements -atomic radii, ionic radii, inert gas radii, Ionization enthalpy, electron gain enthalpy, electronegativity, valency. Nomenclature of elements with atomic number greater than 100.

UNIT IV – Chemical Bonding and Molecular Structure

Valence electrons, ionic bond, covalent bond, bond parameters, Lewis structure, polar character of covalent bond, covalent character of ionic bond, valence bond theory, resonance, geometry of covalent molecules, VSEPR theory, concept of hybridization, involving s, p and d orbitals and shapes of some simple molecules, molecular orbital theory of homonuclear diatomic molecules(qualitative idea only), Hydrogen bond.

UNIT V – Chemical Thermodynamics

Concepts of System and types of systems, surroundings, work, heat, energy, extensive and intensive properties, state functions. First law of thermodynamics – internal energy and enthalpy, measurement of U and H, Hess’s law of constant heat summation, enthalpy of bond dissociation, combustion, formation, atomization, sublimation, phase transition, ionization, solution and dilution. Second law of Thermodynamics (brief introduction)
Introduction of entropy as a state function, Gibb’s energy change for spontaneous and nonspontaneous processes.
Third law of thermodynamics (brief introduction).

UNIT VI – Equilibrium

Equilibrium in physical and chemical processes, dynamic nature of equilibrium, law of mass action, equilibrium constant, factors affecting equilibrium – Le Chatelier’s principle, ionic equilibrium- ionization of acids and bases, strong and weak electrolytes, degree of ionization,
ionization of poly basic acids, acid strength, concept of pH, hydrolysis of salts (elementary idea), buffer solution, Henderson Equation, solubility product, common ion effect (with illustrative examples).

UNIT VII – Redox Reactions

Concept of oxidation and reduction, redox reactions, oxidation number, balancing redox reactions, in terms of loss and gain of electrons and change in oxidation number, applications of redox reactions.

UNIT VIII – Organic Chemistry: Some basic Principles and Techniques

General introduction, classification and IUPAC nomenclature of organic compounds. Electronic displacements in a covalent bond: inductive effect, electromeric effect, resonance and hyper conjugation. Homolytic and heterolytic fission of a covalent bond: free radicals, carbocations, carbanions, electrophiles and nucleophiles, types of organic reactions.

UNIT IX – Hydrocarbons

Classification of Hydrocarbons
Aliphatic Hydrocarbons:
Alkanes – Nomenclature, isomerism, conformation (ethane only), physical properties, chemical reactions.
Alkenes – Nomenclature, structure of double bond (ethene), geometrical isomerism, physical properties, methods of preparation, chemical reactions: addition of hydrogen, halogen, water, hydrogen halides (Markovnikov’s addition and peroxide effect), ozonolysis, oxidation, mechanism of electrophilic addition.
Alkynes – Nomenclature, structure of triple bond (ethyne), physical properties, methods of preparation, chemical reactions: acidic character of alkynes, addition reaction of – hydrogen, halogens, hydrogen halides and water.

Aromatic Hydrocarbons:

Introduction, IUPAC nomenclature, benzene: resonance, aromaticity, chemical properties: mechanism of electrophilic substitution. Nitration, sulphonation, halogenation, Friedel Craft’s alkylation and acylation, directive influence of functional group in monosubstituted benzene. Carcinogenicity and toxicity.

To know the CBSE Syllabus for all the classes from 1 to 12, visit the Syllabus page of CBSE. Meanwhile, to get the Practical Syllabus of Class 11 Chemistry, read on to find out more about the syllabus and related information in this page.

CBSE Class 11 Chemistry Practical Syllabus with Marking Scheme

In Chemistry subject, practical also plays a vital role in improving their academic scores in the subject. The overall weightage of Chemistry practical mentioned in the CBSE Class 11 Chemistry syllabus is 30 marks. So, students must try their best to score well in practicals along with theory. It will help in increasing their overall academic score.

CBSE Class 11 Chemistry Practical Syllabus

The experiments will be conducted under the supervision of subject teacher. CBSE Chemistry Practicals is for 30 marks. This contribute to the overall practical marks for the subject.

The table below consists of evaluation scheme of practical exams.

Evaluation Scheme	Marks
Volumetric Analysis	08
Salt Analysis	08
Content Based Experiment	06
Project Work	04
Class record and viva	04
Total	30

CBSE Syllabus for Class 11 Chemistry Practical

Micro-chemical methods are available for several of the practical experiments. Wherever possible such techniques should be used.

A. Basic Laboratory Techniques
1. Cutting glass tube and glass rod
2. Bending a glass tube
3. Drawing out a glass jet
4. Boring a cork

B. Characterization and Purification of Chemical Substances
1. Determination of melting point of an organic compound.
2. Determination of boiling point of an organic compound.
3. Crystallization of impure sample of any one of the following: Alum, Copper Sulphate, Benzoic Acid.

C. Experiments based on pH

1. Any one of the following experiments:

Determination of pH of some solutions obtained from fruit juices, solution of known and varied concentrations of acids, bases and salts using pH paper or universal indicator.
Comparing the pH of solutions of strong and weak acids of same concentration.
Study the pH change in the titration of a strong base using universal indicator.

2. Study the pH change by common-ion in case of weak acids and weak bases.

D. Chemical Equilibrium
One of the following experiments:

1. Study the shift in equilibrium between ferric ions and thiocyanate ions by increasing/decreasing the concentration of either of the ions.
2. Study the shift in equilibrium between [Co(H₂O)₆] ²⁺ and chloride ions by changing the concentration of either of the ions.

E. Quantitative Estimation
i. Using a mechanical balance/electronic balance.
ii. Preparation of standard solution of Oxalic acid.
iii. Determination of strength of a given solution of Sodium hydroxide by titrating it against standard solution of Oxalic acid.
iv. Preparation of standard solution of Sodium carbonate.
v. Determination of strength of a given solution of hydrochloric acid by titrating it against standard Sodium Carbonatesolution.

F. Qualitative Analysis
1) Determination of one anion and one cation in a given salt
Cations‐ Pb²⁺, Cu²⁺, As³⁺, Al³⁺, Fe³⁺, Mn²⁺, Ni²⁺, Zn²⁺, Co²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mg²⁺, NH₄ ⁺
Anions – (CO₃)^2‐ , S^2‐, NO₂^‐ , SO₃^2‐, SO^2‐ , NO ^‐ , Cl^‐ , Br^‐, I‐, PO₄^3‐ , C₂O²‐ ,CH₃COO^‐
(Note: Insoluble salts excluded)

2) Detection of ‐ Nitrogen, Sulphur, Chlorine in organic compounds.

G) PROJECTS
Scientific investigations involving laboratory testing and collecting information from other sources.

A few suggested projects are as follows:

Checking the bacterial contamination in drinking water by testing sulphide ion
Study of the methods of purification of water.
Testing the hardness, presence of Iron, Fluoride, Chloride, etc., depending upon the regional
variation in drinking water and study of causes of presence of these ions above permissible
limit (if any).
Investigation of the foaming capacity of different washing soaps and the effect of addition of
Sodium carbonate on it.
Study the acidity of different samples of tea leaves.
Determination of the rate of evaporation of different liquids Study the effect of acids and
bases on the tensile strength of fibres.
Study of acidity of fruit and vegetable juices.

Note: Any other investigatory project, which involves about 10 periods of work, can be chosen with the approval of the teacher.

Practical Examination for Visually Impaired Students of Class 11

Below is a list of practicals for the visually impaired students.

A. List of apparatus for identification for assessment in practicals (All experiments)
Beaker, tripod stand, wire gauze, glass rod, funnel, filter paper, Bunsen burner, test tube, test tube stand,
dropper, test tube holder, ignition tube, china dish, tongs, standard flask, pipette, burette, conical flask, clamp
stand, dropper, wash bottle
• Odour detection in qualitative analysis
• Procedure/Setup of the apparatus

B. List of Experiments A. Characterization and Purification of Chemical Substances
1. Crystallization of an impure sample of any one of the following: copper sulphate, benzoic acid
B. Experiments based on pH
1. Determination of pH of some solutions obtained from fruit juices, solutions of known and varied
concentrations of acids, bases and salts using pH paper
2. Comparing the pH of solutions of strong and weak acids of same concentration.

C. Chemical Equilibrium
1. Study the shift in equilibrium between ferric ions and thiocyanate ions by increasing/decreasing
the concentration of eitherions.
2. Study the shift in equilibrium between [Co(H2O)6]2+ and chloride ions by changing the
concentration of either of the ions.

D. Quantitative estimation
1. Preparation of standard solution of oxalic acid.
2. Determination of molarity of a given solution of sodium hydroxide by titrating it against standard
solution of oxalic acid.

E. Qualitative Analysis
1. Determination of one anion and one cation in a given salt
2. Cations – NH+4
Anions – (CO3)2-, S2-, (SO3)2-, Cl-, CH3COO-
(Note: insoluble salts excluded)
3. Detection of Nitrogen in the given organic compound.
4. Detection of Halogen in the given organic compound.

Note: The above practicals may be carried out in an experiential manner rather than recording observations.

We hope students must have found this information on CBSE Syllabus useful for their studying Chemistry. Learn Maths & Science in interactive and fun loving ways with ANAND CLASSES (A School Of Competitions) App/Tablet.

Frequently Asked Questions on CBSE Class 11 Chemistry Syllabus

How many units are in the CBSE Class 11 Chemistry Syllabus?

There are 9 units in the CBSE Class 11 Chemistry Syllabus. Students can access various study materials for the chapters mentioned in this article for free at ANAND CLASSES (A School Of Competitions).

What is the total marks for practicals examination as per the CBSE Class 11 Chemistry Syllabus?

The total marks for the practicals as per the CBSE Class 11 Chemistry Syllabus is 30. It includes volumetric analysis, content-based experiment, salt analysis, class record, project work and viva.

Which chapter carries more weightage as per the CBSE Syllabus for Class 11 Chemistry?

The organic chemistry chapter carries more weightage as per the CBSE Syllabus for Class 11 Chemistry.