6. Which one of the following sequence of the chemical elements is correct in terms of the descending order of atomic radius ?

1. 1. B - C- N - O

   
   
   

   2. C -B - O - N

   
   
   

   3. N - O - B - C

   
   
   

   4. O - N - C - B

   
   
   

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   NA

   Correct Option: A

   NA

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7. The most common lanthanide is

1. 1. Lanthanum

   
   
   

   2. Cerium

   
   
   

   3. Plutonium

   
   
   

   4. Samarium

   
   
   

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   NA

   Correct Option: B

   NA

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8. The elements with atomic numbers 2, 10, 18, 36, 54 and 86 are all

1. 1. Inert gas

   
   
   

   2. Light metals

   
   
   

   3. Halogens

   
   
   

   4. Rare earth metals

   
   
   

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   NA

   Correct Option: A

   NA

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9. Which noble gas does not have octet of electrons in its outer shell ?

1. 1. He

   
   
   

   2. Rn

   
   
   

   3. Ar

   
   
   

   4. None of these

   
   
   

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   NA

   Correct Option: A

   NA

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10. The long form of periodic table consists of

1. 1. 8 Horizontal and 7 vertical series

   
   
   

   2. 7 Horizontal and 18 vertical series

   
   
   

   3. 7 Horizontal and 7 vertical series

   
   
   

   4. 3 Horizontal and 7 vertical series

   
   
   

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   NA

   Correct Option: B

   NA

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