CBSE Class 9 Chemistry-Structure of an Atom (2)

Scroll down for PDF

CBSE Class 9 Chemistry-Structure of an Atom (2). Learning the important concepts is very important for every student to get better marks in examinations. The concepts should be clear which will help in faster learning. The attached concepts made as per NCERT and CBSE pattern will help the student to understand the chapter and score better marks in the examinations. 



1. Energy of electron in H-atom, En = -2.18 x 10 -18 / n2 Jatom-1

2. Energy of electron in H-like species atomEn = -2.18 x 10 -18 z2 / n2 Jatom-1

3. Angular momentum of electron, mvr = nh/2π

4. de- Broglies wavelength, λ = h / mv or λ = h / p

5. Plank’s equation E = hϑ

6. Einstein equation , E = mc2

7. Wave number( )=1/ λ = RH[1/n12 – 1/n22]

8. Isotopes: These are the atoms of the same element having the same atomicnumber but different mass number.e g 1H1,1H2,1H3

9. Isobars: Isobars are the atoms of different elements having the same massnumber but different atomic number.

e g 18Ar40 , 20Ca40 

10. Isoelectronic species: These are those species which have the same numberof electrons.

11. Electromagnetic spectrum:-It is a continuous spectrum. It consists of a range of electromagnetic radiations arranged in the order of increasing wavelengths or decreasing frequencies.

12. Spectroscopy:-The study of emission or absorption spectra is referred as spectroscopy.

13. o Emission spectrum: The spectrum of radiation emitted by a substance that has absorbed energy is called an emission spectrum.

14. o Absorption spectrum : The spectrum obtained when radiation is passed through a sample of material. The sample absorbs radiation of certain wavelengths. The wavelengths which are absorbed are missing and come as dark lines.

15. Bohr’s model for hydrogen atom:

a. An electron in the hydrogen atom can move around the nucleus in a circular path of fixed radius and energy. These paths are called orbits orenergy levels. These orbits are arranged concentrically around the nucleus.

b. As long as an electron remains in a particular orbit, it does not lose or gain energy and its energy remains constant.

c. When transition occurs between two stationary states that differ in energy, the frequency of the radiation absorbed or emitted can be calculated

d. An electron can move only in those orbits for which its angular momentum is an integral multiple of h/2π The radius of the nth orbit is given by    rn =52.9 pm x n2 /Z  energy of electron in nth orbit is ;

Please click the link below to download pdf file for CBSE Class 9 Chemistry-Structure of an Atom (2)


Click on the text For more study material for Chemistry please click here - Chemistry

Latest NCERT & CBSE News

Read the latest news and announcements from NCERT and CBSE below. Important updates relating to your studies which will help you to keep yourself updated with latest happenings in school level education. Keep yourself updated with all latest news and also read articles from teachers which will help you to improve your studies, increase motivation level and promote faster learning

CBSE postpones class 12 English Exam

CBSE had to postpone the class 12 English Exam, the date for the exam will be announced soon. Please see CBSE notice below

CBSE postpones class 12 exams in Delhi

The Central Board of Secondary Education (CBSE) on Wednesday postponed the board examination of standard XII scheduled for Thursday, that is, on the 27th February 2020 for the areas of north - east Delhi affected by communal riots. The rescheduled date for the exam is...

Checking of Boards Answer Sheets Notice

As you all are aware that the boards exams have been postponed due to Corona Virus. You can refer to the notification issued by CBSE too. While the board exams were going on the checking of answer sheets were also going on. CBSE took really good measures to increase...

CBSE class 12 Board examination pattern

This year the Central Board of Secondary Education (CBSE) made some important changes to the Class 12 exam pattern. Students should be aware of every minute detail of the modified exam pattern, from adding the internal exam in all subjects to changing the format of...

CBSE has asked teachers to prepare study material

As CBSE has issued instructions for all teachers to stay at home, CBSE has also issued fresh instructions for teachers to prepare study material for students. CBSE has asked teachers to prepare online study material including videos which can be shared with students....

CBSE Exam centre locator Mobile App

The CBSE board examinations will start from 15 February 2020. The CBSE Board issued admit cards, and all schools start distributing copies of the admit cards. All students should read their admit card details correctly. CBSE admit card details the examination centre,...

Studies Today