Aufbau Principle and filling of electrons in orbitals and sub shells

The Aufbau Principle is a concept used to explain the electronic configuration of atoms. The principle states that electrons occupy the lowest available energy levels in an atom, from lowest to highest energy. While no single scientist is credited with discovering this principle, it has been referenced by many scientists over time and continues to be fundamental in understanding atomic structure. Aufbau Principle for electronic configuration is not on the name of any scientist as usually happened in sciences. Aufbau means building up.

Electrons are build up in orbitals of different subshells of different energy levels on the basis of energy.

Electrons first fill lower energy level and then move to next higher level.

So electrons start filling from 1s orbital on wards in the following sequence:

1s,2s,2p , 3s,3p,4s,3d,4p,5s,4d,5p,6s,4f,5d,6p,7s,5f,6d,7p,8s

Simply it can be learned as ssp sps dps dps fdps fdps

Atomic Number	Element	Electronic Configuration
1	Hydrogen	Is1
2	Helium	Is2
3	Lithium	1s2 2s1
4	Beryllium	1s2 2s2
5	Boron	1s2 2s2 2p1
6	Carbon	1s2 2s2 2p2
7	Nitrogen	1s2 2s2 2p3
8	Oxygen	1s2 2s2 2p4
9	Fluorine	1s2 2s2 2p5
10	Neon	1s2 2s2 2p6
11	Sodium	1s22s22p63s1
12	Magnesium	1s22s22p63s2
13	Aluminium	1s22s22p63s23p1
14	Silicon	1s22s22p63s23p2
15	Phosphorus	1s22s22p63s23p3
16	Sulphur	1s22s22p63s23p4
17	Chlorine	1s22s22p63s23p5
18	Argon	1s22s22p63s23p6
19	Potassium	1s22s22p63s23p64s1
20	Calcium	1s22s22p63s23p64s2
21	Scandium	1s22s22p63s23p64s2 3d1
22	Titanium	1s22s22p63s23p64s2 3d2
23	Vanadium	1s22s22p63s23p64s2 3d3
24	Chromium	1s22s22p63s23p64s1 3d5
25	Manganese	1s22s22p63s23p64s2 3d5
26	Iron	1s22s22p63s23p64s2 3d6
27	Cobalt	1s22s22p63s23p64s2 3d7
28	Nickel	1s22s22p63s23p64s2 3d8
29	Copper	1s22s22p63s23p64s1 3d10

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