Electron Configuration of an element tells us how electrons are filled inside various orbitals of the atom. The distribution of electrons inside various orbital of atoms is very useful in explaining various properties of the atoms and their combination with other atoms.

The electron configuration of the N (the most common element in the Earth’s atmosphere) is 1s² 2s² 2p⁴  as it has 7 electrons which are arranged in order as 2 is 1s orbital, 2 in 2s orbital, and 3 in 2p orbital.

Let’s have a look at how electrons are arranged around a nucleus for other atoms which rules are useful in achieving the right electron configuration and other in this article.

Electron Configuration

The representation of electrons distributed in atomic shells of an element is known as electronic configuration. The electrons are mathematically located in these subshells and the notations help in locating the position of these electrons as well as the electronic configuration. 

An effective study of these electronic configurations written with specific notation can provide details about the particular element. For example, the specific notation for germanium (Ge) would be,1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p².

Notation of Electron Configurations

Notation is the representation of the number of electrons present in the subshell. It is written with the shell number, name of the subshell, and a total number of electrons present in the subshell in superscript.

For example, the electronic configuration of Oxygen can be written as 1s² 2s² 2p⁴.

The following image shows the notation of Electron Configurations.

The below table consists of the electronic configuration of the first 20 elements.

Atomic  Number	Name of  Elements	Electronic Configuration
1	Hydrogen	1s1
2	Helium	1s2
3	Lithium	1s2 2s1
4	Beryllium	1s2 2s2
5	Boron	1s2 2s2 2p1
6	Carbon	1s2 2s2 2p2
7	Nitrogen	1s2 2s2 2p3
8	Oxygen	1s2 2s2 2p4
9	Fluorine	1s2 2s2 2p5
10	Neon	1s2 2s2 2p6
11	Sodium	1s2 2s2 2p6 3s1
12	Magnesium	1s2 2s2 2p6 3s2
13	Aluminum	1s2 2s2 2p6 3s2 3p1
14	Silicon	1s2 2s2 2p6 3s2 3p2
15	Phosphorus	1s2 2s2 2p6 3s2 3p3
16	Sulfur	1s2 2s2 2p6 3s2 3p4
17	Chlorine	1s2 2s2 2p6 3s2 3p5
18	Argon	1s2 2s2 2p6 3s2 3p6
19	Potassium	1s2 2s2 2p6 3s2 3p6 4s1
20	Calcium	1s2 2s2 2p6 3s2 3p6 4s1

Distribution of Electrons in Atomic Orbits

The planetary model of an atom was created by Neils Bohr. He was the first to indicate that the properties of the elements have a regular pattern.

The electronic structure of an atom is based on the “Bohr atomic model.” He was the first to describe the arrangement of electrons in distinct orbits/shells (electronic configuration).

He proposed that electrons are spread in electronic shells that are circular in shape (orbits). These electrons travel a defined distance around the nucleus in orbits. 

Before understanding the concept of Electronic Configuration, let’s first understand some basic terms used with it as mentioned below:

Shells

It is based on the principal quantum number (n)  which determines the maximum number of electrons that can be placed in a shell. The number of electrons in each shell is given by the formula 2n2 where n represents the shell number.

Subshells

It is based on an azimuthal quantum number which is widely denoted by ‘I’.  At the same time, the azimuthal quantum number depends on the value of the principal quantum number (n). For example, if the value of shell n=3.

The subshells corresponding to it will be s,p, and d with I=0, I=1, and I=2. These are the shells in which the actual distribution of electrons takes place. And the maximum number of electrons accommodated by a sub-shell is given by the formula 2(2I+1).

The possible subshells and their resulting electronic configuration based on quantum number are given below.

Value of principal quantum number	Azimuthal quantum number	Electronic configuration
n=1	I=0	1s
n=2	I=0	2s
	I=1	2p
n=3	I=0	3s
	I=1	3p
	I=2	3d
n=4	I=0	4s
	I=1	4p
	I=2	4d
	I=3	4f

Filling of Atomic Orbitals

How atomic orbital are filled with electrons? the answer to this is very important to find the electron configuration of various atoms various rules which help in filling of atomic orbital are,

Aufbau Principle

The principle states that the electrons will occupy the orbits with lower energy and then the orbits with higher energy levels. The principle gets its name from the Greek word “Aufbeen” which means building up. As per the following principle the electrons are arranged in the order as shown in the following image.

Pauli Exclusion Principle

The Pauli Exclusion Principle states that a maximum of two electrons can fit into an orbit with opposite spins. It is based on the concept that if two electrons carry equal azimuthal numbers then they will have opposite spins in the orbit.

Hund’s Rule

The rule states that every orbit is initially occupied by a single electron before a second electron fills the orbit. It’s the rule that determines the order of electrons in the sub-shell.

The following image shows the correct way to fill electrons in a sub-shell. 

Writing Electron Configurations

So, before drawing an electronic configuration we need to extract some information from the periodic table like the atomic number, no. of electrons, shells, etc. Looking through an example let’s understand the writing method of an electronic configuration. The potassium element has atomic number 19. And has 19 electrons which will be placed in s and p sub-shell. 

The electronic configuration can be written as 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹. Its 19 electrons can be divided into different shells in a manner,

• K shell (n=1)= 2,
• L shell (n=2) =8,
• M shell (n=3)=8, and
• N shell (n=4)=1.

Electronic Configuration of Elements

Electronic configuration represents the way in which electrons are filled inside the orbital of any atom. Electronic configuration of various elements are,

Electronic Configuration of Copper

Atomic Number of Copper is 29 and its electronic configuration is,

1s² 2s² 2p⁶ 3s² 3p⁶  3d¹⁰ 4s¹

or

[Ar]3d¹⁰ 4s¹

Electronic Configuration of Chromium

Atomic Number of Chromium is 24 and its electronic configuration is,

1s² 2s² 2p⁶ 3s² 3p⁶  3d⁵ 4s¹

or

[Ar]3d⁵ 4s¹

Electronic Configuration of Oxygen

Atomic Number of Oxygen is 8 and its electronic configuration is,

1s² 2s² 2p⁴

or

[He]2p⁴

Electronic Configuration of Nobel Gases

Ideal gas are chemical elements that have completed valance shells and they generally do not participate in the bonding process. Ideal gas includes Helium, Neon, and others.

Following are the electronic configuration of some ideal gases,

Helium (He): Helium has 2 electrons and its electronic configuration is1s²

Neon (Ne): Neon has 10 electrons and its electronic configuration 1s² 2s² 2p⁶

Argon (Ar): Argon has 18 electrons and its electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁶  

Krypton (Kr): Krypton has 36 electrons and its electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶

Xenon (Xe): Xenon has 54 electrons and its electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶

Radon (Rn): Radon has 86 electrons and its electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁶

FAQs on Electronic Configuration

Q1: Which electronic configuration of an atom is the smallest in size?

Answer:

The atom smallest in size is Hydrogen(H) and its electronic configuration is, 1s¹.

Q2: Who discovered electronic configuration?

Answer:

The electronic configuration of the elents was first done by the Danish physicist Niels Bohr.

Q3: Why the electronic configuration of Niobium is 4d⁴ 5s¹?

Answer:

Energy Gap between 4d and 5s orbital of Niobium is 1.64eV.which signifies that the valence orbitals of Nb are very close to each other and the electrons from electron fromthese orbitals can easily jump among these orbital and thus it have electronic configuration of 4d⁴ 5s¹.

Q4: How electronic configuration is written?

Answer:

The standard notation of writing the electronic configuration of the atom is by writing the shell along with its respective orbitals and then adding the number of elections in them in the superscript. Example, 1s¹ signifies that it has 1 electron is its s orbital of 1 shell.

Q5: Why the electronic configuration of Chromium(24) is different?

Answer:

The general electronic configuration of chromium should be, 1s² 2s² 2p⁶ 3s² 3p⁶  3d⁴ 4s² but, the actual electronic configuration is, 1s² 2s² 2p⁶ 3s² 3p⁶  3d⁵ 4s¹ this is because the half filled d orbital is more stable than 3d⁴ orbital configuration. So the electron from 4s orbital jumps to 3d orbital to gain extra stability,

Q6: Why the electronic configuration of Copper(29) is different?

Answer:

The general electronic configuration of cpooer should be, 1s² 2s² 2p⁶ 3s² 3p⁶  3d⁹ 4s² but, the actual electronic configuration is, 1s² 2s² 2p⁶ 3s² 3p⁶  3d¹⁰ 4s¹ this is because the full filled d orbital is more stable than 3d⁹ orbital configuration. So the electron from 4s orbital jumps to 3d orbital to gain extra stability,

Q7: List the significance of electronic configuration.

Answer:

The significance are mentioned below:

1. They help to know the reactivity state of the atom.
2. It helps to determine its physical as well as chemical properties.
3. It predicts an atom’s magnetic behavior, etc.

Q8: How many electrons does each of the sub-shells hold?

Answer:

The electron filling pattern in subshells is:

• s holds 2 electrons
• p holds 6 electrons
• d holds 10 electrons
• f holds 14 electrons

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.

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

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.