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Electron Configuration and Energy Level Diagrams

Note: Before proceeding, it is important to keep the following in mind. According to quantum mechanics:

Electrons do not “occupy” orbitals. Nor do orbitals “contain” electrons.
Electrons do not “fill” orbitals one at a time. Nor do electrons have properties that designate individual electrons as first, second, third, fourth, etc.
Orbitals do not really have substance or shapes. Orbitals, recall, are mathematical equations that can be used to calculate probability densities for electrons. The shapes, and the impression of substance, result from the contour lines used to set a limit on the extent of those probabilities.

Creating Energy-Level Diagrams

Our interpretation of atomic spectra is that electrons in an atom have different energies. The fine structure of the atomic spectra indicates energy sublevels. The designation of these energy levels has been by quantum number. Now we are going to use energy-level diagrams to indicate which orbital energy levels are occupied by electrons for a particular atom or ion. These energy-level diagrams show the relative energies of electrons in various orbitals under normal conditions

When creating the energy level diagrams you have to remember the following:

You show an electron in an orbital by drawing an arrow, pointed up or down to represent the electron spin. It does not matter if you point the arrow up or down in any particular circle, but two arrows in a circle must be in opposite directions. This is really a statement of the Pauli exclusion principle.
Electrons (arrows) are placed into the orbitals by filling the lowest energy orbitals first. An energy sublevel must be filled before moving onto the next higher sublevel.This is called the aufbau principle.
If you have several orbitals at the same energy (e.g.,p,d,or f orbitals), one electron is placed into each of the orbitals before a second electron is added. This rule is called Hund’s rule.

Steps:

Start adding electrons into the lowest energy level (1s) and build up from the bottom until the limit on the number of electrons for the particle is reached — the aufbau principle.
No two electrons can be put into the same orbital of equal energy until one electron has been put into each of the equal-energy orbitals — Hund’s rule

Examples:
O – Oxygen has 8 electrons to be placed into the energy level diagram

1s ↓↑ 2s ↓↑ 2p ↓↑ ↑ ↑

Pb – lead has 82 electrons to place into the energy level diagram

1s ↓↑ 2s ↓↑ 2p ↓↑ ↓↑ ↓↑ 3s ↓↑ 3p ↓↑ ↓↑ ↓↑ 4s ↓↑ 3d ↓↑ ↓↑ ↓↑ ↓↑ ↓↑ 4p ↓↑ ↓↑ ↓↑ 5s ↓↑ 4d ↓↑ ↓↑ ↓↑ ↓↑ ↓↑
5p ↓↑ ↓↑ ↓↑ 6s ↓↑ 4f ↓↑ ↓↑ ↓↑ ↓↑ ↓↑ ↓↑ ↓↑ 5d ↓↑ ↓↑ ↓↑ ↓↑ ↓↑ 6p ↓↑ ↑ ↑

Es – Einsteinium has 99 electrons

1s ↓↑ 2s ↓↑ 2p ↓↑ ↓↑ ↓↑ 3s ↓↑ 3p ↓↑ ↓↑ ↓↑ 4s ↓↑ 3d ↓↑ ↓↑   ↓↑ ↓↑ ↓↑ 4p ↓↑ ↓↑ ↓↑ 5s ↓↑ 4d ↓↑ ↓↑ ↓↑ ↓↑ ↓↑
5p ↓↑ ↓↑ ↓↑ 6s ↓↑4f ↓↑ ↓↑ ↓↑ ↓↑ ↓↑ ↓↑   ↓↑ 5d ↓↑ ↓↑   ↓↑ ↓↑ ↓↑ 6p ↓↑ ↓↑ ↓↑ 7s ↓↑
5f ↓↑ ↓↑ ↓↑ ↓↑   ↑   ↑   ↑     ↑