Electronic Configuration

Every member of Group 2 carries two electrons in the outermost s-orbital, giving the general configuration $[noble\ gas]\,ns^2$:

• Be: $1s^2\,2s^2$
• Mg: $1s^2\,2s^2\,2p^6\,3s^2$
• Ca: $1s^2\,2s^2\,2p^6\,3s^2\,3p^6\,4s^2$
• Sr: $[Kr]\,5s^2$
• Ba: $[Xe]\,6s^2$
• Ra: $[Rn]\,7s^2$ …