Write the complete ground-state electron configuration of Ag.
The Correct Answer and Explanation is:
Ground-state electron configuration of silver (Ag):
Ag:[Kr] 4d10 5s1\text{Ag}: [Kr]\, 4d^{10}\, 5s^1Ag:[Kr]4d105s1
Explanation
Silver (Ag) has an atomic number of 47. This means it has 47 electrons in its neutral ground state. To write the electron configuration, we start from hydrogen and fill orbitals in the order prescribed by the Aufbau principle, which prioritizes lower-energy orbitals first. The general order of filling is:
1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p, and so on.
Following this order, you would expect the electron configuration of silver to be:
[Kr] 4d9 5s2[Kr]\, 4d^9\, 5s^2[Kr]4d95s2
However, the actual configuration is:
[Kr] 4d10 5s1[Kr]\, 4d^{10}\, 5s^1[Kr]4d105s1
This occurs due to a phenomenon related to electron stability. A fully filled or half-filled subshell offers extra stability due to symmetrical distribution and exchange energy. In the case of silver, moving one electron from the 5s orbital to complete the 4d orbital gives a full 4d^10 configuration, which is more stable than the expected 4d^9 5s^2 arrangement.
This irregularity is similar to what we see in other elements such as copper (Cu), which has an electron configuration of [Ar] 3d^10 4s^1 instead of the expected [Ar] 3d^9 4s^2. In both cases, a filled d-subshell offers a lower energy state overall.
Using the noble gas shorthand, we begin with [Kr], the electron configuration for krypton, which accounts for the first 36 electrons. The remaining 11 electrons fill the orbitals as 4d^10 and 5s^1. This results in the most stable and experimentally observed ground-state configuration for silver.
Understanding such exceptions is important for explaining physical and chemical properties such as atomic size, ionization energy, and bonding behavior.
