Question

3. What is the electron configuration of an electrically neutral atom of sodium?
What is the electron configuration of an electrically neutral atom of neon?
What is the electron configuration of an electrically neutral atom of oxygen?

Answer 1

Sodium is in period 3, so it is before the complications of the d orbital that arise in period 4. It is in group 1, so it will have an electron configuration of \[1s^2 2s^2 2p^6 3s^1\]
Neon comes before the complications of the d orbital as well, and it is the last element in period 2. This means it will complete the p orbital. So: \[1s^2 2s^2 2p^6\]
Oxygen is period 2 group 16. It will fill up 4 of the six spaces in the d orbital, so:
\[1s^2 2s^2 2p^4\]

Answer 2

Na - 1s2 2s2 3p6 1s2
Ne - 1s2 2s2 3p6
O - 1s2 2s2 3p4