Electron Orbitals Electrons fill atomic orbitals in a very particular way, moving from the nucleus out. The orbitals / electrons closest to the nucleus have the lowest energies, thus they are filled first. As more and more electrons are added, they must go to higher and higher energy levels. With each increasing main energy level within an atom we find more and more orbitals with more sub-levels. The simplest kind of orbital is the s-orbital. It is shaped like a sphere. The next type of orbital is the p-orbital. The p-orbitals are dumbbell-shaped and are found on each of the three major axes of the atom, x, y, and z. Each of the above orbitals is capable of holding only 2 electrons.

Sketch these figures.

So, the s-orbital holds only 2 electrons. When it is filled, the next electron must go to a higher energy orbital. Each of the p-orbitals holds two electrons. So the total electrons held in sublevel p is 6. Likewise, since the d-orbital has 5 configurations, its maximum capacity is 10 electrons. The “Diagonal Rule” is a “map” showing us the order that electron orbitals are filled and become occupied.

s s 3p 3d s 2p s 4p 4d 4f s 5p 5d 5f 5g? s 6p 6d 6f 6g? 6h? s 7p 7d 7f 7g? 7h? 7i? Diagonal Rule Steps: 1.Write the energy levels top to bottom. 2.Write the orbitals in s, p, d, f order. Write the same number of orbitals as the energy level. 3.Draw diagonal lines from the top right to the bottom left. 4.To get the correct order, follow the arrows! Diagonal Rule Steps: 1.Write the energy levels top to bottom. 2.Write the orbitals in s, p, d, f order. Write the same number of orbitals as the energy level. 3.Draw diagonal lines from the top right to the bottom left. 4.To get the correct order, follow the arrows! By this point, we are past the current periodic table so we can stop. Electrons per orbital

Electron Configurations – Examples from PowerPoint Packet H (1e-) 1s 1 Li (3e-) 1s 2 2s 1 Ne (10e-) 1s 2 2s 2 2p 6 K (19 e-) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 Zn (30 e-) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 Pb (82 e-) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 2 Note that the electron configuration contains the energy level (period / row) in which the element is found in the periodic table. Example: The highest energy level in krypton’s electron configuration is 4 (4s 1 ), and krypton is found in period 4 of the periodic table. 4s 1 means main energy level 4 and 1 electron in the s-orbital. Note that the 1 is NOT an exponent.