Write the electronic configuration of a neutral copper atom. - Leaving Cert Chemistry - Question b - 2002

The electronic configuration of a neutral copper atom (Cu), which has an atomic number of 29, can be written as follows:

1. Start with the filling of the 1s orbital:

   • $1s^2$

2. Progress to the 2s and 2p orbitals:

   • $2s^2$ and $2p^6$

3. Continue to the 3s and 3p orbitals:

   • $3s^2$ and $3p^6$

4. Filling now goes to the 4s orbital:

   • $4s^2$

5. For the d-orbitals, instead of filling $3d^{10}$ before $4s^2$, copper exhibits a special case where it has a configuration of:

   • $3d^{10}$ and $4s^1$

Thus, the complete electronic configuration combines these orbitals:

$1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10}$

Alternatively, it can also be expressed using noble gas notation:

$[Ar] 3d^{10} 4s^1$