CBSE ASSIGNMENT CLASS – X Chapte - CARBON AND ITS COMPOUNDS

Q 1. Justify the nature of physical and chemical properties of the compound of homologous series -2
CBSE 2013-14

A Homologous Series is a group of organic chemical compounds, usually listed in order of increasing size, that have a similar structure (and hence also similar properties) and whose structures differ only by the number of CH2 units in the main carbon chain.

1. Chemical Properties

Organic compounds that are part of the same homologous series generally have similar chemical properties as each other, due to the presence of the same functional group in the molecules of all compounds in the series.

2. Physical Properties

The physical property of any particular member of a homologous series depends on its size, or its position within the homologous series. The physical properties, such as solubility, melting point, boiling point, specific gravity etc. show a gradual change with the increase in their relative molecular masses.

Q 2. Apart from organic being where else we find carbon? Mention the form in which it is available there and also its percentage CBSE 2013-14
Ans: Apart from organic being we find carbon in the earth’s crust about 0.02% in the form of minerals like carbonates, hydrogen carbonates, coal and petroleum CBSE 2013-14

Q3. How are carboxylic acids different from mineral acid on the basis of ionization point of view? CBSE 2013-14
Ans: Carboxylic acids are weak acids and do not ionised completely where as mineral acids like HCl ionised completely.

Q5. Write chemical equation to describe different oxidations of ethanol. CBSE 2013-14

Ans: Ethanol is oxidized to ethanoic acid with alkaline KMnO4 or acidified K2Cr2O7

CH3CH2OH ----Oxidation---> CH3COOH (Ethanoic acid) + H2O

During this reaction, orange colour of K2Cr2O7 changes to green. Therefore, this reaction can be used for the identification of alcohols.
Practice assignment

1. Covalent compounds do not undergo  _____.

2. The property of _______ of carbon atoms to form long chains is called catenation.

3. A group of structurally similar compounds , each member of which differs from preceding or succeeding member CH2  group is called ____.

4. What will happen if a piece of diamond is dropped in a charcoal fire?

5. The form of carbon which is used as a lubricant at high temperature is _________.

6. What is the valency of carbon in (a) Methane  (b) Ethene  (c) ethyne?

7. Compounds of carbon and hydrogen alone are called _________.

8. The hydrocarbons containing a triple bond are known as _________.

9. The organic compounds containing –OH as the functional group are known as __________.

10. In carboxylic acids the functional group is _________.

11. Compounds having same functional group have almost identical __________properties.

12. Isomers have same ________formula and different  _________ formula.

13. The next homologue of C2H5OH is ______.

14. What is the general formula of the homologous series of Alkynes and Alcohols?

15. An organic compound A is a constituent of wine. This compound on heating with Alkaline Potassium permanganate solution gets oxidized to give another compound B which turns blue litmus red. Identify A and B. Write their chemical names and chemical formulae.

16. How will you distinguish between Hard and Soft water?

17.Give any two advantages of Detergents over soaps

18. Besides  Carbon name the other elements which show the phenomenon of Allotropy.

19. How many electron pairs are shared in :
      a) Single covalent bond 
      b) Double covalent bond 
      c) Triple covalent bond

20.(a) Explain with the help of chemical equation the following properties of carbon compounds-

(i) Combustion (ii) Oxidation

(b) How do saturated and unsaturated hydrocarbons can be differentiated on the basis of their combustion?

(c) What are oxidizing agents ? 

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Water 'A precious resources' CBSE Class VI Science

Q. Why are we left only tiny fraction of water for use even if about 75 % of the earth surface is covered with water.
Ans: This is because most of the water about 97% of surface water is in sea and ocean as salty water that is unfit for domestic and agricultural use.
Q. What are the various uses of water?
Ans: Water is used for various activities such as agriculture, industries, cooking, cleaning utensils,
bathing, washing clothes, and, most importantly, for drinking.
Q. What are the three state of water?

Ans: There are three states of water
a. Solid state: ice, snow and hail           b. liquid: Rain, river, sea   c. Gaseous: Water vapour
Q what is water cycle?
Ans: The circulation of water from atmosphere to the earth and vice versa is called the water cycle.
Q.What is evaporation?
Ans: The water present on the surface of the ocean evaporates by the sun’s heat. This process of conversion of water from liquid state to vapour state is called evaporation.
Q what is transpiration?
Ans: The excess water in plants evaporates through stomata of leaves and the stem into the air. This process is called transpiration.
Q. How cloud is formed?
Ans: The evaporated water above the earth surface is carried away by warm air. As the warm air moves higher from the surface of the Earth, it starts to cool down. It is because the water vapour present starts to condense to form tiny water droplets. These droplets float in the air and form cloud
Q. What is precipitation?
Ans: When clouds rub together heat is produced that melt the cloud into droplets. These droplets collect to form bigger drops of water. Some of them may become too heavy fall down as rain. This process is known as precipitation.
Q .What do you mean by infiltration?
Ans: The water from rain, rivers, lakes and ponds seeps through the soil and fills the space below the ground. The process of seeping of water through the soil is called infiltration
Q. What do you mean by aquifer?
Ans: Some places groundwater is stored between layers of hard rock. This is called aquifer. Water from aquifers is pumped and taken out through hand pumps and tube wells.
Q. How can we conserve water?
Ans: Water conservation is process of preventing wastage of water, using water carefully and recharging ground water. Water conservation can be done by :-
i) Repairing leaking pipes and taps.        
ii) Not wasting water during brushing teeth, shaving, bathing, washing clothes and during other activities.
iii) Rainwater harvesting.      
iv) By drip irrigation of plants.
Q. Fill in the blanks with the appropriate answers:
(a) People obtain ---------through tube wells and hand pumps.[groundwater]
(b) Three forms of water are solid, liquid and ---------[vapour.]
(c) The water bearing layer of the earth is ----------[ aquifer]
(d) The process of water seepage into the ground is called ---------[ infiltration.]
(e) The process of changing of water into its vapour is called---------[ evaporation.]
(f) The process of changing water vapour into water is called ---------[condensation.]
(g) No rainfall for a year or more may lead to ---------- in that region.[drought]
(h) Excessive rains may cause ----------- [flood.]

CBSE Class 7 Solved Objective Questions Chapter - Acids, Bases and Salts (MCQs)

CBSE Class 7 Solved Objective Questions  Chapter - Acids, Bases and Salts MCQs

1. The word acid comes from the Latin word ------ which means sour.( acere)

2. The substances used to test whether a substance is acidic or basic are known as ----(indicators)

3. The most commonly used natural indicator is litmus paper . It is extracted from ----(lichens)

4. In acidic solution, litmus paper turns into ------(red)

5. In basic solution, litmus paper turns into ------(blue)

6. In distilled water , litmus paper turns into ------(purple)

7. China rose indicator turns acidic solutions ------and basic solutions to ------ [dark pink (magenta) , green]

8. The reaction between an acid and a base is known as ----- [neutralization]

9. Salt and water are produced in neutralization process with the evolution of heat.[ water]

10. H C l + N a O H ---->      ------- + H2O

11. Our stomach contains -------. It helps us to digest food[hydrochloric acid]

12. indigestion is painful so to relieve indigestion, we take an antacid such as milk of magnesia , which contains ------- [magnesium hydroxide]

13. The sting of an ant contains ---------[ formic acid]

14. The effect of the sting can be neutralized by rubbing moist baking soda (sodium hydrogen carbonate) or calamine solution, which contains ------- [zinc carbonate]

15. When the soil is too acidic, it is treated with ---------------[ bases like quick lime (calcium oxide) or slaked lime (calcium hydroxide)]

16. Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. its nature ---------------------- [Basic]

17. The wastes of many factories contain-------- [ acids]

18. Blue litmus paper is dipped in a solution. It remains blue. -------- is the nature of the solution. [basic]

19. Proteins that build part of our cells are made up of------ [amino acids]

20. The fats in our body contain ------ [fatty acids]

21. Each cell in our body contains an acid called ---------- [the deoxyribonucleic acid]

22. ----------- is common to all acids?[hydrogen ion]

23. ------ gas evolved when dilute sulphuric acid acts on sodium carbonate[CO2]

24. Acids do not show acidic behavior in absence of water because ------ dissociates from an acid only in in presence of water .[ hydrogen ions]

25. ---- base is also used in soda-acid fire extinguishers.[ Baking Soda]

26. -------- gas is usually liberated when an acid reacts with a metal [ H2]

27. The hydrogen ions combine with H2O to form ------------- [ hydronium ions (H3O+)]

28. Aqueous solution of acid conduct electricity due to -------- present in it. [ ion]

29. ------------ is the common name of the compound CaOCl2 [Bleaching powder]

30. -------------- is Universal Indicator [ pH Scale]

31. pH is the measure of Acidity or Alkalinity of a solution. The term pH stands for ----------[“Potential of hydrogen”]

32. If the pH rain water drops below ----------------. it is called acid rain[5.6]

33. The bases that dissolve in water are known as -----------[ alkalies]

34. Aqueous solution of sodium chloride (NaCl) is known as -------------[ Brine]

35. Salts containing water molecules in their crystal form are called --------- [hydrated salts]

36. water molecules present in salt s known as ------------ [‘water of crystallization’]

37. Phenolphthalein become colourless in ---- and pink in ------[ Acid, base]

38. --------- is the colour of methyl orange in acidic solution.[ pink]

39. ------------ and ------- acid are present in vinegar and lemon.[ acetic acid, citric acid]

X Chemistry Ch - 05 Periodic Classification of Elements CBSEQuestions Bank

1 mark questions:- Question from Board papers

1. What is the name given to group of three similar elements by Dobereiner?

2. State "Newlands law of Octaves" for classification of elements.

3. Name the fundamental property used by Mendeleev as the basis of classification.

4. How many groups and periods are there in the Modern periodic table?

5. What was the prediction of Mendeleev regarding the gaps in his periodic table?

6. How is valence of an element determined?

7. What will be the valence of an element having atomic number 16?

8. How does valence vary in going down a group?

9. Why inert gases have zero valences?

10. What would be the valence of an atom containing 8 electrons in its outermost shell?

11. How does the electronegative character of elements vary along a period of the periodic table?

12. The present classification of elements is based on which fundamental property of elements?

13. Among first ten elements in the modern periodic table name the metals present.

14. Metals are on which side of Modern periodic table?

15. State Mendeleev’s periodic law.

16. Name two elements, other than Gallium, whose existence was predicted by Mendeleev.

17. State Modern Periodic law.

18. Write the name given to the vertical columns in a periodic table.

19. What name is given to the horizontal rows in a periodic table?

20. Why does silicon is classified as Metalloid?

2 marks question:-

21. State two limitations of Newland's law of Octaves.

22. Name the scientist who proposed modern periodic law? On which fundamental property of elements it is based?

23. Why could no fixed position be given to hydrogen in Mendeleev’s Periodic table?

24. What are metalloids? Give two examples.

25. In group 1 of periodic table three elements X, Y and Z have atomic radii 133 pm , 95pm and

65pm respectively giving a reason, arrange them in the increasing order of their atomic number in

the group.

26. In modern periodic table, the isotopes of Chlorine Cl-35 and Cl-37 having different atomic

masses will be kept in different slots or they would be assigned same position on the basis of their

chemical properties? Give reason in support of your answer.

27. Nitrogen (At no. 7) and Phosphorus (At no. 15) belong to group 15 of the periodic table:-

(i) Write the electronic configuration of the two.

(ii) Predict whether they are metallic or nonmetallic in nature.

28. How and why does the atomic size vary as you go down a group?

29. Why was Dobereiner system of classification of elements into triads not found to be useful?

3 marks questions:-

30. State three merits of Modern periodic table.

31. What are amphoteric oxides? Choose the amphoteric oxide from among the following oxides :–  Na2O, ZnO, Al2O3, CO2, H2O

32. Study the variation in the atomic radii of first group elements given below and arrange them in increasing order :–

Group I element                     Na     Li        Rb           Cs          K

Atomic Radii P.M                  86     152     244          262        231

33. An element X has the electronic configuration as 2, 8, 7 :–

(a) What is the atomic number of the element?

(b) What will be the formula of its compound formed with Na?

(c) What is the name given to the family of this element?

34. How do you calculate the valence of the element from its electronic configuration?  What  is

the valence   of Mg with atomic number 12 and sulphur with atomic number 16? How does the 

valence vary in going down in a group?

35. Atomic radii of the elements of the period II are as follows:–

Period II elements :      Be  B  O  N  C  Li

Atomic Radius :  111  88  66  74  77  152

(i) Arrange them in decreasing order of their atomic radii.

(ii) How does the atomic size vary on moving from left to right in a period? Explain why?

(iii) How will the tendency to lose electrons will vary on moving from left to right in this period II?

36. Oxygen (O, 8) and sulphur (S, 16) belong to group 16 of the periodic table:-

(i) Write the electronic configuration and valence of these two elements?

(ii) Which among these will be more electronegative? Why?

37. The positions of three elements A, B and C in the periodic table are given below:-

(i) State element C is a metal or nonmetal.

(ii) Which is smaller B or C and why?

(iii) Which type of ion will be formed by A, B and C?

5 marks questions:-

38. Two elements ‘A’ and ‘B’ belong to group 1 and 2 respectively in the same period.

Compare them with respect to :–

(a) Number of valence electrons.      (b) Valency               (c) Metallic character                                     
(d) Size of atom                               (e) Formulae of their oxides.

39. From the table answer the following questions:–

(a) Write the formulae of chloride of A.

(b) What is the electronic configuration of ‘S’?

(c) Name the noble gas.

(d) Write the formula of compound which carbon forms with G.

(e) What name is given to the family of group 17 element?

40.An element X (atomic number 17) reacts with an element Y (atomic number 20) to form a divalent halide.
(a) Where in the periodic table are elements X and Y placed?
(b) Classify X and Y as metal (s), non-metal (s) or metalloid (s).
(c) What will be the nature of the oxide of element Y? Identify the nature of bonding in the compound formed.
(d) Draw the electron dot structure of the divalent halide.

CBSE Board : Class X Guess (Physics + Chemistry) SA_II With Solution

Questions
1. Why carbon forms strong bonds with other carbon atoms, hydrogen, oxygen, nitrogen or sulphur?

2. Name the part of eye responsible for conversion of light into electrical impulses.

3.  a. How does valency vary in a group on going from top to bottom?      
b. How does atomic size vary in a period on going from left to right?

4. Write one property of hydrogen which makes it resemble with (a) Alkali metals (b) Halogens.

5. (a) Arrange the following common substances in the increasing order of refractive indices. Ice, Kerosene, Glass, Diamond, Alcohol, Water(b) Is it necessary that optically dense medium possesses greater mass density? Give an example.

6. On reaction with sodium hydroxide, X yielded Ethanoic acid and ethanol.(a) Give the IUPAC name of X?   
(b) Name the reaction. 
 (c) Give a chemical reaction for the above reaction.

7. (a) How does the electronic configuration of an atom related to its position in the Modern periodic table? Give one example.(b) Why nitrogen is more electronegative than phosphorus?

8. A concave length has focal length of 25 cm. At what distance should the object from the lens be placed so that if it forms an image at 20 cm distance from the lens? Also find the magnificationproduced by the lens.

9. Give an explanation for the formation of a rainbow.

10.  How are we able to see distant and near by objects clearly? Which part of eye helps in changing curvature of lens? Why no image is formed at blind spot?

11.(a) Why magnification is taken negative for real images and positive for virtual images? (2)(b) Why convex mirror is used in rear view mirrors and not concave mirror? (2)(c) Power of concave lens is 4.5 D. Find its focal length. (1)

12. (a) Find the size, nature and position of image formed when an object of 1 cm is placed at a distance of 15 cm from a concave mirror of focal length 10 cm. (3)(b) Why does light travels faster in water in comparison to kerosene. (Refractive index of water and kerosene are 1.33 and 1.44 respectively)  (2)

13 . a. Which property of carbon leads to formation of large number of compounds? Define itb. What is the functional group in the following molecules? i.  CH₃CH₂CH₂OH     ii.   CH₃COOHc. Which of the following formula represents a saturated hydrocarbon?C_nH _2n, C _nH_2n+1 C_n H_2n+2 C_n H_2n-2
d. What happens when methane is burnt in oxygen?e. Why is the conversion of ethanol to Ethanoic acid an oxidation reaction?                                      

14. a. Give three points to distinguish between alkenes and alkynes.b. Explain the mechanism of cleaning action of detergents

SAMPLE PAPER(solution)

1. Due to small size and presence of four valence electrons, carbon forms strong bonds with other carbon atoms, hydrogen, oxygen, nitrogen or sulphur. 

2. Retina. 

3. a. Valency remains same on moving from top to bottom in a particular group. This is because the outermost electronic configuration of all the elements in a group remains same. 
b. Atomic size decreases on moving from left to right in a period. This is because the number of shells remains same but the nuclear charge increases. Due to this, electrons are pulled closer to the nucleus and decrease the atomic size. 

4. Resemblance with alkali metals:  
Hydrogen has the same outermost electronic configuration as that of alkali metals.
Resemblance with halogens:
Hydrogen exists as diatomic molecule as halogens. 

5. a. In the order of increasing refractive indices:
Ice; Water; Alcohol; Kerosene; Glass; Diamond                                           
b. No, it is not always necessary.  For e.g., kerosene and turpentine oil having high refractive index are optically dense than water. But its mass density is less than that of water. That is why oil floats on the surface of water. 


6. (a) X is ethyl  Ethanoate.                
(b) It is Saponification reaction.                                  
(c) CH₃COOC₂H₅ + Na OH ----------->  C₂H₅OH + CH₃COOH                             1


7. (a) By the electronic configuration of an atom we can identify the group and period to which the atom belongs. 
For example - Oxygen has atomic number 8. Its electronic configuration is 2,6.  As it can gain two electrons to complete its octet, so it belongs to group 16 Also, since the electrons are filled in two shells. So. Oxygen belongs to the second period.                                                     


(b) As we move down the group, electro negativity of elements decreases as  the atomic size increases. Nitrogen is placed above phosphorus in group 15. So, nitrogen is more electronegative than phosphorus.        
8. A concave lens always forms a virtual, erect image on the same side of the object.
v = -20 cm, f = -25 cm, u = ?              
1/v -1/u = 1/f         
1/u = 1/(-20) – 1/(-25)         
1/u = -1/100     
u= -100cm       
Thus object distance is 100 cm.          
Magnification= v/u 
= -20/ (-100) 
= + 0.5 1  
Thus image is erect, virtual and is half of the size of object.               


9. Formation of rainbow: 
The rainbow is formed in the sky when sun shines and it is raining at the same time. The raindrops in the atmosphere act like many small prisms.        
As white light enters and leaves these raindrops the various colours present in white light are refracted by different amount due to which an arch of seven colours called rainbow is formed in the sky.      

Diagram [self]                 


10. (a) Accommodation   (b) Ciliary muscles.  (c) No image is formed at the blind spot because no nerve cells are present there to carry the information of image to the brain.  

11. (a) Distance measured upward and perpendicular to the principal axis are  taken as positive.  Distances measured down ward and perpendicular to the principal axis are  taken as negative.   So magnification for a real image is taken negative and for a virtual image it is taken as positive.    

(b) A convex lens forms a virtual and small sized image of the object and concave mirror forms real and inverted image.    
Thus by using convex mirror we can get view of wider field which is not possible in case of a concave mirror. 
(c) Power = 1/Focal length     Or Focal length = 1/Power       
 f= 1/4.5      so, f = 0.22 cm 1         


12.   (a) Object distance, u = -15 cm      Image distance, v= ?   Focal length, f = -10 cm
Mirror formula,    
 1/v + 1/u = 1/f        
1/v + 1/ (-15) = 1/(-10)      
1/v = -1/10 + -/15   
1/v = -3+2/30      
1/v = -(1/30)    
Thus the position of image is formed on left hand side in front of the concave mirror at a distance of
30 cm, its nature will be real and inverted.      
          
Size of image m= -v/u            m = - [(-30)/(-15)]          m = -2.
Thus the size of image is 2 cm and image is real and inverted.        
  
(b) Refractive index of a medium= Speed of light in air/ Speed of light in medium.
So, speed of light in medium= speed of light in air/ refractive index                        
Thus speed of light will be maximum in medium having lowest refractive   index. Therefore speed of light is more in water in comparison to kerosene.             


13. (a) Catenation
The property of carbon atom to link with other carbon atoms to form large molecules is called as catenation. 
(b).   i. Functional group is –OH group.          
      ii. Functional group is –COOH group.        
(c) C_n H_2n+ 2 represents a saturated hydrocarbon.     
(d) Methane burns in oxygen with formation of carbon dioxide and water.           
CH₄ + 2O₂ ----------->  CO₂ + 2H₂O                                                                                      
(e.) Conversion of ethanol to Ethanoic acid is an oxidation reaction because  oxygen is added to ethanol and Ethanoic acid is formed.                   
CH ₃CH₂ OH + O₂   ----------->         CH₃ COOH        +       H₂ O
 Ethanol                                               Ethanoic acid                                             


14.[a]. No. Alkene                
(1) Unsaturated hydrocarbon containing a double bond between two carbon atoms are known as alkenes.  
(2) General formula is     C_nH_2n            
 Example: Ethene, Propene               
Alkynes: Unsaturated hydrocarbons containing a triple bond between two carbon atoms are known as alkynes. 
(2) General formula is C_nH_2n -2        
(3) Example:  Ethyne, Propyne            


b. A detergent molecule consists of two ends – 
(a) hydrocarbon tail which is hydrophobic (water repelling) and 
(b) polar head which is hydrophilic (water attracting or loving). 

When a detergent is dissolved in water, the hydrocarbon tail aligns itself towards the dirt and ionic part aligns itself towards the water. The molecules gather together as clusters, called micelles. 

When water is agitated, the dirt suspended in the micelles is easily rinsed away. Thus, the cloth gets cleaned.

How was the neutron discovered? (Structure of Atom)

1932: English physicist James Chadwick publishes a letter on the existence of the neutron. His discovery helps clear the way for splitting the nuclei of even the heaviest atomic elements, making possible the development of the atomic bomb.

Unlike the proton, the other large subatomic particle that helps form the nucleus of an atom, the neutron contains no electric charge. This enables it to pass through the electric barrier of heavy atoms to penetrate and split their nuclei, the basis of the nuclear chain reaction.

Chadwick studied various problems related to radioactivity under Nobel laureate (and proton-discoverer) Ernest Rutherford at the University of Manchester before going to Germany to work with Hans Geiger at the Physikalisch-Technische Reichanstalt (Imperial Physical-Technical Institution) in Berlin. He was in the German capital when World War I began.

As an enemy alien, Chadwick was interned by the Germans, but allowed to set up a laboratory in the stables of his civilian internee camp outside Berlin. He remained there throughout the war, doing his research, before returning to Britain in 1919.

Working again with Rutherford, who had by this time moved to Cambridge University, Chadwick helped his mentor achieve the first artificial nuclear transformation. They also achieved the transmutation of other light elements by bombarding them with alpha particles, while pressing ahead with research into the basic structures of the atomic nucleus.

Chadwick's discovery of the neutron — posited by Rutherford 12 years earlier — was made while he was still at Cambridge. It led to the fission of uranium 235, the key element used in the development of the atomic bomb. Regarding his achievement, Chadwick remarked with some ambivalence that he now realized that the development of an atomic weapon was not only likely, but inevitable.

During World War II, Chadwick came to the United States as part of the British delegation working on the Manhattan Project.

For his discovery of the neutron, Chadwick was first awarded the Hughes Medal by the Royal Society in 1932 and, three years later, the Nobel Prize for Physics.

Characteristics of a neutron

(i) Mass of a neutron: Mass of a neutron is equal to that of a proton.

Thus , mass of a neutron = 1.676 ×10^-27 kg= 1.676 ×10^-24g

(ii) Charge on a neutrons = Neutrons do not carry any electrician charge. So, neutrons are neutral particles.

Source: Nobelprize.org

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