Science chapter11

Answer very briefly. 

1. Name an element which has the same number of electrons in its first and second shell. 

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2. Write the electronic configuration of K and Cl 

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3. Write down the names of the particles represented by the following symbols and explain the meaning of superscript and subscript numbers attached.

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4. For an atom ‘X’, K, L and M shells are completely filled. How many electrons will be present in it? 

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5. What is the same about the electron structures of: 

a. Lithium, Sodium and Potassium.  

b. Beryllium, Magnesium and Calcium.

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Answer briefly. 

1. How was it shown that atom has empty space?

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2. Why do Cl-35 and Cl-37 have the same chemical properties? In what respect do these atoms differ? 

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3. Draw the structure of oxygen and sulphur atoms. 

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4. Calculate the number of neutrons, protons and electrons: 

(i) atomic number 3 and mass number 7 

(ii)atomic number 92 and mass number 238. 

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5. What are nucleons? How many nucleons are present in Phosphorous? Draw its structure.

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Answer in detail. 

1. What conclusions were made from the observations of Gold foil experiment? 

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2. Explain the postulates of Bohr’s atomic model. 

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3. State the Gay Lussac’s law of combining volumes. Explain with an illustration.

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