Question

Why does calcium only have 8 electrons in the third shell?

Answer 1

Answer:

This principle states that, “Electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. In this way, the electrons of an atom or ion form the most stable electron configuration possible.” ... This is the reason for Calcium to have a configuration of 2,8,8,2 instead of 2,8,10

Explanation:

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Answer 2

Answer:

Calcium :

Atomic number : 20

Electronic configuration : [Ar]4s^2. or 1s^2 2s^2 2p^6 3s^2 3p^6. 4s^2

In configuration of 3rd period electrons can be filled up to 3p6 orbitals .

According to aufbau principle:

We can't fill 3d orbital without filling 4s orbital .If we take 4s then it will be 4th period That's why, third period can have 8 electrons having maximum capacity of holding 18 electrons.