Question

How many electrons are in the n = 2 shell of the oxygen atom before bonding?

Answer 1

Answer: 6 electrons

Explanation: Oxygen atom has atomic no of 8 which means it has got 8 electrons. n=2 depicts that the electrons have principle quantum no = 2. According to Afbau's rule the electrons are arranged in shells of increasing energy as follows:

$O(8)-1s^22s^22p^4$

Thus there are 2 electrons in 2s and 4 electrons in 2p which makes a total of 6 electrons.

Answer 2

6 electrons are in then 2nd shell, this is because oxygen has 8 electrons and two are already in the first shell leaving only 6 left to go into the 2nd shell