Electron configuration

[Juliana Logan 1A]

Why is the electron configuration for Ag [Kr] 4d10 5s1? I thought that the 5s subshell filled up first so why isn't it [Kr] 4d9 5s2?

[Samantha Miceli 3J]

From my understanding, the reason it is [Kr] 4d10 5s1 and not [Kr] 4d9 5s2 is because 9 electrons in the d orbital is just one electron away from having a full orbital. Because it is so close, there is a tendency for one of the 5s electrons to fill the 4d orbital, bringing it to 10 electrons. Looking at the periodic table, Cu, which has the same #of valence electrons as Ag, also follows this pattern. Cu: [Ar] 3d10 4s1

[vincent_loyal]

Since Silver is in the same Group as Copper, which Professor Lavelle said was an exception to how the orbitals filled up, it is also another exception.