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Feb 12, 2014 · The Chemistry of Love Essay Sample, Example. Love has been referred to as a sublime feeling as long as written literature has existed. Poets, philosophers, artists, and other representatives of creative professions sought for its origins, reasons, and recipes. However, in the 21st century, people have become pragmatic enough to assume that love ...
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Class 9 > All Useful Links. Download Class 9 Chemistry, Chapter 4 Notes, Structure of Molecules that contains MCQ's, Long Q, Exercise Q, Numerical in PDF for free.
CBSE Class 9, Chemistry, Sample Papers . Atoms and Molecules; Structure of Atom; Is Matter Around Us Pure; Matter In Our Surroundings
CL provides CBSE Chemistry prep material for class 9 students. Get free Key Notes, MCQs, Tests, Sample Papers, NCERT Solutions, NCERT Solutions, Important Questions for 9.
- Introduction to The Structure of An Atom
- Radioactivity
- Rutherford Model
- Be More Curious!!!
- Neil Bohr Model
Atoms
To know more about Atomic Structure, visit here.
Cathode Ray Experiment
1. J. J. Thomson discovered the existence of electrons. 2. He did this using a cathode ray tube, which is a vacuum-sealed tube with a cathodeand anode on one end that created a beam of electrons travelling towards the other end of the tube. 3. The air inside the chamber is subjected to high voltage, and electricity flows through the air from the negative electrode to the positive electrode. 4. The characteristics of cathode rays (electrons) do not depend upon the material of electrodes and th...
Electrons
1. Electrons are the negatively charged sub-atomic particles of an atom. 2. The mass of an electron is considered to be negligible, and its charge is -1. 3. The symbol for an electron is e– 4. Electrons are extremely small. 5. They are found outside the nucleus.
Radioactivity
1. Radioactivity is the term for the process by which an unstable nucleus of an atom loses energy by giving out particles. 2. It does so by giving out particles such as alpha and beta particles. 3. This process is spontaneous. 4. An atom is unstable if the nucleus has an imbalance, meaning a difference in the protons and neutrons. To know more about Radioactivity, visit here.
Rutherford’s Experiment and Observations
In this experiment, fast-moving alpha (α)-particles were made to fall on a thin gold foil. His observations were: 1. A major fraction of the α-particles bombarded towards the gold sheet passed through it without any deflection, and hence most of the space in an atom is empty. 2. Some of the α-particles were deflected by the gold sheet by very small angles, and hence the positive charge in an atom is not uniformly distributed. 3. The positive charge in an atomis concentrated in a very small vo...
Rutherford’s Model of an Atom
Rutherford concluded the model of the atom from the α-particle scattering experiment as follows: (i) There is a positively charged centre in an atom called the nucleus. Nearly all the mass of an atom resides in the nucleus. (ii) The electrons revolve around the nucleus in well-defined orbits. (iii) The size of the nucleus is very small compared to the size of the atom.
Drawbacks of Rutherford’s Model
1. He explained that the electrons in an atom revolve around the nucleus in well-defined orbits. Particles in a circular orbit would experience acceleration. 2. Thus, the revolving electron would lose energy and finally fall into the nucleus. 3. But this cannot take place as the atom would be unstable, and the matter would not exist in the form we know.
The Millikan’s Oil Drop Experiment was an experiment performed by Robert A. Millikan and Harvey Fletcher in 1909 to measure the charge of an electron.In the experiment, Millikan allowed charged tiny oil droplets to pass through a hole into an electric field.By varying the strength of the electric field, the charge over an oil droplet was calculated, which always came as an integral value of ‘e.’The conclusion of this is that the charge is said to be quantized, i.e. the charge on any particle will always be an integral multiple of e which is 1.6*10-19Properties of Electrons, Protons and Neutrons
Bohr’s Model of an Atom Bohr came up with the following postulates to overcome the objections raised against Rutherford’s model. 1. Electrons revolve around the nucleus in stable orbits without the emission of radiant energy. Each orbit has a definite energy and is called an energy shell or energy level. 2. An orbit or energy level is designated as K, L, M, and N shells. When the electron is in the lowest energy level, it is said to be in the ground state. 3. An electron emits or absorbs ener...
Orbits
Orbits are energy shells surrounding the nucleus in which electrons revolve.
Electron Distribution in Different Orbits
The distribution was suggested by Bohr and Bury. 1. The maximum number of electrons present in a shell is given by the formula 2n2, where ‘n’ is the orbit number or energy level index, 1,2,3,…. 2. The maximum number of electrons in different shells are as follows: the first orbit will have 2*12=2, the second orbit will have 2*2Msup>2=8, the third orbit will have 2*32=18, the fourth orbit 2*42=32 and so on. 3. The shells are always filled in a step-wise manner from the lower to higher energy l...
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By practising these Class 9 important questions, students will be able to quickly review all of the ideas covered in the chapter and prepare for the Class 9 Annual examinations. Download Class 9 Chemistry Chapter 4 – Structure of the Atom Important Questions with Answers PDF by clicking on the button below.
In this post, I am sharing Class 9 Chemistry Chapter 4 Short Questions Notes for students. Structure of Molecules is the 4th Chapter in the 9th Chemistry textbook. From ilmihub, students can download these 9th Class Chemistry Chapter 4 Short Questions Notes in PDF format. These Chemistry 9th class chapter 4 notes are for all the boards working ...
