Why?????

Asked by gujralhsk | 4th Oct, 2009, 06:16: PM

Expert Answer:

This is true that the maximum number of electrons in M shell can be 18 according to the formula 2n2

But in calcium, there are 8 electrons in the M shell. In potassium also, there are 8 electrons in the M shell.

This is because of the rule that " The outermost shell cannot have more than 8 eletcrons."

So, now if we take the example of calcium , and write its configuration as 2,8,10 :: Then the outermost shell of calcium will be M shell and it will have 10 electrons which will violate the rule. So, the configuration of calcium is 2,8,8,2.

SImilarly for potassium, if we write its configuration as 2,8, 9  :: Then the outermost shell of potassium will be M shell and it will have 9 electrons which will again violate the rule. So, the configuration of potassium is 2,8,8,1.

 

Answered by  | 5th Oct, 2009, 09:52: AM

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