When writing electronic configuration, never put space or punctuation between the orbit and orbital denotations. 1s 2s 2p 3s3p 4s3d4p5s4d5p6s4f5d6p7s5f6d7p.įigure 1: The Aufbau diagram presents that electrons are added to each orbital starting at 1S orbital until all electrons have occupied their unique position. Likewise, the arrows indicate the direction in which the electrons occupy orbitals along the direction they are pointing to, e.g. However, orbitals within one principal energy level can overlap orbitals of another resulting in a unique order of orbital energy levels as portrayed in Figure 1 (Huheey, Keiter, Keiter, & Medhi, 2006).įigure 1 shows the order of atomic orbitals by energy level. Likewise, s orbital has lower energy than p followed by d and f orbit. Also, only two electrons can be placed per orbital where all orbitals of a sublevel are placed at equal energy levels. electrons will first fill the 1s orbital before occupying 2s orbital in its ground state. It states that the electrons must occupy the lowest energy orbital first, i.e.
The Aufbau principle serves as a starting point to determine the electronic configuration of an atom or ion.
In cases where two orbitals share same (n+l) value, then orbital with lower ‘n’ value is associated with lower energy level (Singh, 2011). Hence, lower (n+l) values depict lower orbital energy. The sum of these numbers determines the energy level of the orbital in question.
This order of assembly can be derived using (n+l) rule, also called Madelung rule where ‘n’ stands for principal quantum number and ‘l’ stands for the angular quantum number. The word ‘Aufbau’ is derived from the German word ‘ Aufbauprinzip’ that can be roughly translated to ‘build up’ or ‘assemble’.
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