Question

Write electronic configurations of the elements (number in the brackets indicate atomic numbers)
oxygen $\left(8\right)$

Answer 1

Oxygen is the eighth element with a total of 8 electrons. In writing the electron configuration for oxygen the first two electrons will go in the 1s orbital. Since $1s$ can only hold two electrons the next 2 electrons for $O$ go in the $2s$ orbital. The remaining four electrons will go in the $2p$ orbital. Therefore the O electron configuration will be $1s^{2}2s^{2}2p^4$.