Let's look at a Copper(II) ion with 6 water molecules around it. Step 1: Count the electrons in the d-orbitals of Copper(II). It has 9 electrons (d9). Step 2: Fill the 'rooms' (orbitals). We have two types of rooms: lower energy (t2g) and higher energy (eg). Step 3: We put 6 electrons in the lower rooms and 3 electrons in the higher rooms. Step 4: Notice the higher rooms (the eg set). One room has 2 electrons, but the other only has 1. This is 'lopsided'. Step 5: Because it is lopsided, the atom feels uncomfortable. Step 6: To feel better, the atom stretches the bond with the two ligands on the top and bottom. The shape becomes an elongated octahedron.