Toppers Study Toppers Study Toppers StudyGet CBSE Notes for Class 9 Science – 4. Structure of The Atom: Electronic Configuration And valency. Clear, exam-focused notes with key concepts, formulas & solved examples.
CBSE Notes for Class 9 Science chapter 4. Structure of The Atom: Electronic Configuration And valency, quick revision notes for Class 9 Science chapter 4. Structure of The Atom Electronic Configuration And valency, Chapter-wise CBSE Revision Notes, CBSE Notes PDF Free Download, CBSE One Liner Notes Class 9, Half Yearly Revision Notes, CBSE Revision Notes Class 9 Science
Get CBSE Notes for Class 9 Science Chapter 4. Structure of The Atom: Electronic Configuration And valency prepared by experts as per the latest NCERT syllabus and CBSE exam pattern. These concise and easy-to-understand notes cover important definitions, formulas, diagrams, and key concepts from the chapter to help students in quick revision and effective exam preparation. Whether you are studying for school tests, board exams, or competitive exams, these notes provide a reliable study resource. Designed in simple language with point-wise explanations, they save time and enhance learning efficiency. Download free PDF notes, explore solved examples, and strengthen your understanding of [Topic Name] for scoring high marks. Perfect for Class 9 students who want clear, structured, and exam-oriented notes for CBSE Science.
Chapter 4. Structure of The Atom
Energy Levels : There are various and definite orbits around the nucleus of an atom to revolve the electrons. These orbits or shells are called energy levels.
Energy Levels in An Atom
Electronic Configuration: The distribution of electrons in various and discrete shells of an atom is known as electronic configuration. The maximum numbers of electrons are difinite in each shell.
The Electronic Structure of Hydrogen:
Hydrogen has only one electron, so that it's outer shell is K and has only one electron.
The Electronic Structure of Carbon Atom:
Carbon atom has total 6 electrons. In which it has 2 electrons in its inner most shell K and 4 electrons in outer most shell L.
These are shells:
K, L, M, N etc.
Number of maximum electron in various shell:
Shell K can have maximum 2 electrons.
Shell L can have maximum 8 electrons.
Shell M can have maximum 18 electrons and
Shell N can have maximum 32 electrons.
There is used a formula to keep maximum electron in each shell : 2n2
On the basis of this formula, the maximum electrons in a shell is found.
Example, For the first shell K : 2(1)2 = 2 x 1 = 2
For the second shell L : 2(2)2 = 2 x 4 = 8
For the third shell M : 2(3)2 = 2 x 9 = 18
For the fourth shell N : 2(4)2 = 2 x 16 = 32
Valency : The number of valence electrons present in outer most shell of an atom is known as valency.
Example:
Electronic configuration of some elements and its valency:
(1) Sodium has 11 electrons,
Electronic configuration of sodium: 2, 8, 1
(2) Oxygen has 8 electrons,
Electronic configuration of Oxygen: 2, 6
Example: If there is 1 electron in outer most shell of atom of an element, then valency will be 1. If outer most shell has 2, 3 or 4 electron then valency will be 2, 3 or 4 respectively. But if outer most shell has 5, 6 or 7 electrons then valency will be find in such manner as follows.
When outer most shell has 5 electrons then valency will be 8 - 5 = 3
When outer most shell has 6 electrons then valency will be 8 - 6 = 2
When outer most shell has 7 electrons then valency will be 8 - 7 = 1
When outer most shell has 8 electrons then valency will be 8 - 8 = 0
Now, See this table:
| Name of Element | Symbol | No. of Atom | No. of protons | No. of Nutrons | No. of Electrons |
Electronic configuration K L M N |
Valency |
| Hydrogen | H | 1 | 1 | - | 1 | 1 | 1 |
| Helium | He | 2 | 2 | 2 | 2 | 2 | 0 |
| Lithium | Li | 3 | 3 | 3 | 3 | 2 1 | 1 |
| Berelium | Be | 4 | 4 | 4 | 4 | 2 2 | 2 |
| Boran | B | 5 | 5 | 5 | 5 | 2 3 | 3 |
| Carbon | C | 6 | 6 | 6 | 6 | 2 4 | 4 |
| Nitrogen | N | 7 | 7 | 7 | 7 | 2 5 | 3 |
| Oxygen | O | 8 | 8 | 8 | 8 | 2 6 | 2 |
| Flourine | F | 9 | 9 | 9 | 9 | 2 7 | 1 |
| Neon | Ne | 10 | 10 | 10 | 10 | 2 8 | 0 |
| Sodium | Na | 11 | 11 | 11 | 11 | 2 8 1 | 1 |
| Magnesium | Mg | 12 | 12 | 12 | 12 | 2 8 2 | 2 |
| Aluminium | Al | 13 | 13 | 13 | 13 | 2 8 3 | 3 |
| Silicon | Si | 14 | 14 | 14 | 14 | 2 8 4 | 4 |
| Phosphoras | P | 15 | 15 | 15 | 15 | 2 8 5 | 3, 5 |
| Sulphar | S | 16 | 16 | 16 | 16 | 2 8 6 | 2 |
| Chlorine | Cl | 17 | 17 | 17 | 17 | 2 8 7 | 1 |
| Argon | Ar | 18 | 18 | 18 | 18 | 2 8 8 | 0 |
Atomic Number: The total Number of protons present in the nucleus of an atom is known as atomic number.
Example - Let be the total number of protons in the nucleus of an atom is 8 then atomic number will be 8. Similarily if the total number of protons is 11 then atomic number that atom will be 11.
Atomic number = Number of protons
Atomic Mass: The sum of total number of protons and nutrons present in the nucleus of an atom is known as atomic Mass.
Example - If an atom has 4 protons and 5 nutrons in its nucleus then atomic mass will be 4 + 5 = 9.
Similarily if an atom has 7 protons and 7 nutrons the atomic mass will be 7 + 7 = 14.
Atomic Mass = No. of protons + No. of Electrons
Note: The number of protons in an atom is equal to the number of electron of an atom. The same number is its atomic number. The number of nutrons may be equal to the number of protons or may not be equal.
For students preparing for board exams or competitive assessments, CBSE notes have become an indispensable tool. These notes summarize the NCERT textbooks, highlighting key concepts, formulas, definitions, and diagrams in a concise and easy-to-understand format. Unlike lengthy textbooks, CBSE notes allow students to focus on the most important points, saving valuable time during revision.
In conclusion, CBSE notes are not just a revision tool—they are a strategy. When used correctly, they help students cover the syllabus efficiently, improve retention, and approach exams with confidence. For exam-going students, the combination of structured notes, practice, and consistent revision is the key to achieving top results.
Ace your exams with CBSE Notes for Class 9 Science chapter 4. Structure of The Atom: Electronic Configuration And valency. These notes provide a clear explanation of important concepts, formulas, diagrams, and solved examples from the NCERT syllabus. Specially designed for Class 9 students, the notes are structured in a simple, point-wise manner to make revision quick and effective. Whether you are preparing for school tests, board exams, or competitive exams, these Science notes will boost your confidence and save valuable study time. You can also download Science class 9 chapter 4. Structure of The Atom free PDF notes for offline learning. With easy-to-grasp language, exam tips, and well-organized content, these CBSE Science notes on chapter 4. Structure of The Atom – Electronic Configuration And valency are the perfect study companion for scoring high marks and mastering the subject.
CBSE class 10 Science notes are available completely free in PDF, and these all notes are quick revising materials that help you prepare for your upcoming board exams. Students can easily access CBSE notes pdf free download class 10 Science and get free CBSE notes class 10 Science notes designed strictly as per the latest NCERT syllabus. These Class 10 CBSE notes and Class 10 Science notes are short, simple, and to the point, making them perfect for last-minute revisions. You can also refer to NCERT book notes for class 10 that cover every chapter in an easy-to-understand manner. With these Quick revision notes Science class 10, you save time while covering all important formulas, definitions, and concepts.
Download worksheets and assignments for better practice and revision.