Halogens are the elements in the periodic table of Group 17 of the periodic table. Fluorine, chlorine, bromine, and iodine are examples of reactive nonmetals. Halogens are nonmetals that are extremely reactive. These elements have a lot in common in terms of properties.
Group 17 elements are known as halogens and include fluorine, chlorine, bromine, iodine, and astatine.
This degree of closeness is not observed in other groupings of the periodic table. They exhibit a consistent gradation of physical and chemical properties. The only radioactive element in the category is astatine. They have seven electrons in their outermost shell and are one electron short of the nearest noble gas configuration. An element’s chemical characteristics and reactivity are determined by the oxidation state it exhibits.
At standard temperature and pressure, the halogen group is the only periodic table group that contains elements in three of the four primary states of matter. When halogens are linked to hydrogen, they all react to generate acids. The majority of halogens are derived from minerals or salts. As disinfectants, the middle halogens—chlorine, bromine, and iodine—are frequently utilised. The most common type of flame retardant is organobromine, but elemental halogens are hazardous and can be lethally poisonous.
Table of Contents
Electronic Configuration of Halogens
These electrons have the electrical configuration ns2 np5 in their valence shell. As a result, these elements have 7 electrons in their outermost shell. By one electron, the element loses out on the octet configuration. As a result, these elements seek to lose one electron and make a covalent link or acquire one electron and establish an ionic bond. As a result, these are highly reactive nonmetals.
Oxidation State of Halogens
The halogen family’s elements all have a -1 oxidation state. Fluorine, the most electronegative element, only has a -1 oxidation state. Elements with +1, +3, +5, and +7 states include chlorine, bromine, and iodine. When chlorine, bromine, and iodine combine with tiny and extremely electronegative fluorine and oxygen atoms, they achieve a higher oxidation state. Chlorine and bromine oxides and oxoacids have +4 and +6 states, respectively. Because the fluorine atom lacks valence shells and d orbitals, it cannot increase its octet.
Physical Properties of Halogens
The elements in group 17 can be found in a variety of physical states. Fluorine and chlorine, for example, are gases. Bromine, on the other hand, is a liquid, whereas Iodine is solid.
These elements are coloured in a number of ways. Iodine, for example, is dark violet in colour, but fluorine is pale yellow.
Water dissolves Fluorine and Chlorine. Bromine and iodine, on the other hand, are very poorly soluble in water.
As we progress down the group from Fluorine to Iodine, the melting and boiling temperatures of these elements increase. Fluorine, as a result, has the lowest boiling and melting points.
Chemical Properties of Halogens
Oxidizing Power: All halogens are excellent oxidizing agents. Fluorine is the most strong oxidising agent on the list. It has the ability to convert all halide particles to halogen. As we advance down the group, the oxidising power decreases. The halide particles also function as reducers. Their decreasing capacity, however, reduces the group as well.
Reaction with Hydrogen: When halogens react with hydrogen, they form acidic hydrogen halides. From HF to HI, the acidity of these hydrogen halides decreases. Fluorine reacts aggressively, and chlorine requires sunlight to function. Bromine, on the other hand, reacts when heated, whereas iodine requires a catalyst.
Reaction with Oxygen: Oxides are formed when halogens react with oxygen. However, it has been discovered that the oxides do not remain stable. Halogens, in addition to oxides, produce a variety of halogen oxoacids and oxoanions. Halogens are highly reactive, forming halides when they react with metals and nonmetals. As we move down the group, their reactivity decreases. Halogens have a high oxidising capacity. F2 is the most powerful oxidising halogen. It easily oxidises other halide ions in solution or in solid form. In general, a halogen oxidises a higher atomic number of halide ions. As an example:
F2 + 2X– → 2F– + X2 (X = Cl, Br or I)
The interactions of halogens with water demonstrate their relative oxidising tendency. Water is oxidised by fluorine to produce oxygen. Whereas chlorine and bromine react with water to generate hydrohalic and hypohalous acids, respectively. Iodine has a non-spontaneous reaction with water. Water in an acidic media can oxidise I–. As an example:
4I– (aq) + 4H+ (aq) + O2 (g) → 2I2(s) + 2H2O (l)
General Characteristics of Halogens
Atomic and Ionic Radii of Halogen Family
Group 17 members have the shortest atomic radii in their respective eras. This is due to the fact that they have the highest effective nuclear charge. Because the number of quantum shells grows from fluorine to iodine, atomic and ionic radii increase from top to bottom in a group.
Ionisation Enthalpy
Members of group 17 have almost no tendency to lose an electron. As a result, they have a very high ionisation enthalpy value. Because of the increase in atomic size, the ionisation enthalpy drops from top to bottom in the group.
Electron Gain Enthalpy
Group 17 atoms are only one electron away from achieving stable noble gas structures. As a result, at the relevant periods, these elements exhibit the highest negative electron gain enthalpy. Because of the increase in atomic size, the electron gain enthalpy of these elements gets less negative as we advance down the group. Chlorine, on the other hand, has a greater negative electron gain enthalpy than fluorine.
Electronegativity
The elements of group 17 have a relatively high electronegativity value. Because of the drop in effective nuclear charge, electronegativity decreases along with the group. Fluorine is thus the most electronegative element.
Uses of Halogens
Fluorine molecules are a significant component of toothpaste. This is because fluoride chemicals react with the enamel of the teeth, preventing tooth decay.
Chlorine is mostly used as bleach. It’s also employed in the production of precious metals like platinum and gold.
Because it kills bacteria on the skin, iodine is used as an antiseptic.
Interhalogen Compounds
Interhalogen compounds are those that result from the reaction of two distinct halogens. They have general compositions of XY, XY3, XY5, and XY7, where X is a bigger size halogen and Y is a smaller size halogen, and X is more electropositive than Y. As the ratio between the radii of X and Y grows, so does the number of atoms per molecule.
Biological role of Halogens
Fluoride anions can be present in animal ivory, bones, teeth, blood, eggs, urine, and hair. Fluoride anions may be necessary for humans in extremely small concentrations. Human blood contains 0.5 milligrammes of fluoride per litre. Fluorine levels in human bones range from 0.2 to 1.2 %. Fluorine is found in around 50 parts per billion in human tissue.
Chloride anions are required by many animals, including humans. The concentration of chlorine in cereals is 10 to 20 parts per million, whereas the concentration of chloride in potatoes is 0.5 %. Chloride levels in the soil that fall below 2 parts per million have a negative impact on plant growth. Human blood contains 0.3 % chlorine on average. Chlorine levels in human bone are normally around 900 parts per million. Human tissue contains between 0.2 and 0.5 % chlorine.
All organisms have some bromine in the form of bromide anion. Although no biological role for bromine in humans has been established, organobromine chemicals are found in several organisms. Bromine is commonly used by humans in amounts ranging from 1 to 20 mg per day. Bromine levels in human blood are normally 5 parts per million, 7 parts per million in human bones, and 7 parts per million in human tissue.
Humans ingest fewer than 100 micrograms of iodine each day on average. Intellectual impairment can result from an iodine deficit. Organoiodine compounds are found in human glands, particularly the thyroid gland, as well as the stomach, epidermis, and immune system. Cod, oysters, shrimp, herring, lobsters, sunflower seeds, seaweed, and mushrooms are all high in iodine. Iodine, on the other hand, is not known to play a biological role in plants.
Sample Questions (FAQs)
Question 1: What are interhalogen compounds?
Answer:
The chemicals generated by the reaction of two distinct halogens are known as interhalogens.
Question 2: What are the oxidation states exhibited by halogens?
Answer:
The halogen family’s elements all have a -1 oxidation state. The most electronegative element, fluorine, has only a -1 oxidation state. Chlorine, bromine, and iodine are examples of elements that have +1, +3, +5, and +7 states.
Question 3: How do halogens react with oxygen?
Answer:
Oxides are formed when halogens react with oxygen. However, the oxides have been discovered to be unstable. Halogens produce a variety of halogen oxoacids and oxoanions in addition to oxides.
Question 4: How does electron gain enthalpy of halogens compares to other groups?
Answer:
Group 17 elements’ atoms are only one electron away from achieving stable noble gas structures. As a result, at the relevant periods, these elements have the highest negative electron gain enthalpy. Due to the increase in atomic size, the electron gain enthalpy of these elements gets less negative as we advance down the group. In comparison to fluorine, however, chlorine has a lower electron gain enthalpy value.
Question 5: Are halogens good oxidizing agents?
Answer:
All of the halogens are excellent oxidizers. Fluorine is the most strong oxidising agent on the list. It has the ability to convert all halide particles to halogen.
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.
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‐ , S2‐, NO2‐ , SO32‐, SO2‐ , NO ‐ , Cl‐ , Br‐, I‐, PO43‐ , 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 theapproval 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
Q1
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).
Q2
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.
Q3
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.
Anand Technical Publishers
Buy Products (Printed Books & eBooks) of Anand Classes published by Anand Technical Publishers, Visit at following link :
