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NEET2012Chemistrys Block ElementsActual

The correct order of decreasing first ionisation energy is

Options

  1. AC B Be Li
  2. BC Be B Li
  3. CB C Be Li
  4. DBe Li B C

Correct answer

B. C Be B Li

Step-by-step solution

On moving from left to right in a period, as the size decreases, ionisation energy increases. But first IE of elements of II A group is higher than that of the elements of III A group because of the stable n s^2 configuration (of II A group). Hence, the order of first ionisation energy is ( array c & C & > & Be & > & B & > & Li Group no. & (IV) & & (II) & & (III) & & (I) array )

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