How each orbital looks like.

Patrick Lim (H3G) and Jan Chan (H3D)

First things first, an orbital is a region of space (in the atom) that is quite close to the nucleus wherein the electron will be found within that easily defined region. There are actually four kinds of orbitals: s, p, d, f orbitals:

  • To differentiate each one of them, one will look at the shape of the orbitals. The s orbital will look like a circle; the p orbital will look like two identical balloons that are tied together at the nucleus; the d orbital look like a four leaf clover wherein the nucleus is found in the center; lastly the f orbitals on the other hand are very complicated and look different from each other.
    • The maximum number of electrons in each orbital:
      • s=2, p=6, d=10, f=14
  • The number of orbitals in each energy level:
    • 1st (includes s orbital)= 2;
    •  2nd (includes s and p orbital) =8;
    • 3rd (includes s, p and d orbital)=18;
    •  4th (includes s, p, d and f orbital)=32

There are three principles behind writing down electron configurations and orbital notations:

  • First, the Pauli Exclusion Principle states that no two electrons can have the same 4 quantum numbers;
  • Another principle followed is the Aufbau principle that simply states that when the electron structure of an atom is being filled with electrons, each new electron is placed closer to the nucleus as it is supposed to be placed on the lowest available energy level;
  •  The other principle followed is the Hand’s rule. It says that when electrons are added to orbitals of the same energy, all the available orbitals must be occupied by an electron first before another electron is added to any occupied orbital to serve as a pair for the earlier added electron on it.

Next, the topic that is going to be tackled is how to write down electron configurations and orbital notations of elements correctly. The sample element to be used  will be Bromine:

  • Step 1: Determine the number of electrons of an atom (in this case Bromine will have 35 electrons)
  • Step 2: Once the number of electrons is determined, fill in the maximum amount of electrons for every orbital based on the electron configuration pattern beginning with 1s^2
  • Step 3: After beginning with 1s2, this will how the electron configuration (in the case of Bromine) will look like: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^5. To check this, when all the superscripts are added, it equates to 35.

The image below will show how to properly write the orbital notation for Bromine:

How to properly right the orbital notation of Bromine.


  1. http://en.wikibooks.org/wiki/Chemical_Principles/Electronic_Structure_and_Atomic_Properties
  2. http://education.jlab.org/qa/electron_number.html
  3. http://www.brightstorm.com/science/chemistry/the-atom/atomic-orbitals/#
  4. http://en.wikibooks.org/wiki/Chemical_Principles/Electronic_Structure_and_Atomic_Properties
  5. http://4.bp.blogspot.com/_DZbDcIFlgfo/TMNdS7o3VEI/AAAAAAAAABw/M31gbHwi_zQ/s1600/image002.jpg
  6. http://www.wikihow.com/Write-Electron-Configurations-for-Atoms-of-Any-Element
  7. http://electronconfiguration.info/

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