Electron Chemistry Example 1

Solution

1. 1
   Oxygen has atomic number 8, so a neutral oxygen atom has 8 electrons. Fill orbitals using the Aufbau principle in order of energy: $1s$, then $2s$, then $2p$.
2. 2
   Fill each subshell to its maximum capacity: $1s^2$ (2 electrons), $2s^2$ (2 electrons), leaving $8 - 4 = 4$ electrons for the $2p$ subshell.
3. 3
   Write the complete electron configuration: $1s^2\,2s^2\,2p^4$. Verify: $2 + 2 + 4 = 8$ total electrons.