Electronic Configuration Example

The electronic configuration is the description of how electrons are organized in an atom. It was initially proposed by Niels Bohr in 1923, who relied on Bohr's atomic model to determine in what order and quantities the electrons were attached to their respective orbitals.

To this day, the Bohr electron configuration is no longer used, as it does not give a reference to the orbitals and the energies that identified them. It was years later that the distribution of electrons in the sublevels and orbitals of an atom was definitively established. The electronic configuration came to be governed by the Moeller diagram, which is the following table:

s	p	d	F
k = 1	1s
l = 2	2s	2 P
m = 3	3s	3p	3d
n = 4	4s	4p	4d	4f
o = 5	5s	5 p	5 d	5f
p = 6	6s	6p	6d	6f
q = 7	7s	7p	7d	7f

The electron configuration notation runs diagonally, from top to bottom and from right to left (shaded and white cells follow). Writing this sequence, it remains:

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

This series is called the construction principle or

Aufbau principle. The electrons of an atom are going to be distributed among all the terms. The number of electrons in an atom is known from the atomic number, represented by the letter Z. For example, the atomic number of hydrogen is 1, so it has one electron. The one for calcium is 20, so it has 20 electrons.

To write the electron configuration, you write the orbital location and, as a superscript, the number of electrons what's in that orbital. In the first instance, the localization is put in the form nl, that is, the principal quantum number "n" followed by the secondary quantum number "l", of that orbital. And as a superscript, the number of electrons there.

Each sublevel, which can be represented by the letters s, p, d,F, has a certain number of electrons that it can contain:

• The s it can hold 2 electrons.
• The p it can hold 6 electrons.
• The d it can hold 10 electrons.
• The F it can hold 14 electrons.

Examples of electron configuration

• Hydrogen (H) (Z = 1): 1s¹
• Helium (He) (Z = 2): 1s²
• Calcium (Ca) (Z = 20): 1s², 2s², 2 P⁶, 3s², 3p⁶, 4s²
• Cesium (Cs) (Z = 55): 1s², 2s², 2 P⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5 p⁶, 6s¹
• Francium (Fr) (Z = 87): 1s², 2s², 2 P⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5 p⁶, 6s², 4f¹⁴, 5 d¹⁰, 6p⁶, 7s¹
• Iron (Fe) (Z = 26): 1s², 2s², 2 P⁶, 3s², 3p⁶, 4s², 3d⁶
• Osmium (Os) (Z = 76): 1s², 2s², 2 P⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5 p⁶, 6s², 4f¹⁴, 5 d⁶
• Mercury (Hg) (Z = 80): 1s², 2s², 2 P⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5 p⁶, 6s², 4f¹⁴, 5 d¹⁰
• Cadmium (Cd) (Z = 48): 1s², 2s², 2 P⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰
• Zinc (Zn) (Z = 30): 1s², 2s², 2 P⁶, 3s², 3p⁶, 4s², 3d¹⁰
• Silicon (Si) (Z = 14): 1s², 2s², 2 P⁶, 3s², 3p²
• Bromine (Br) (Z = 35): 1s², 2s², 2 P⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁵
• Antimony (Sb) (Z = 51): 1s², 2s², 2 P⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5 p³
• Iridium (Ir) (Z = 77): 1s², 2s², 2 P⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5 p⁶, 6s², 4f¹⁴, 5 d⁷
• Carbon (C) (Z = 6): 1s², 2s², 2 P²
• Sulfur (S) (Z = 16): 1s², 2s², 2 P⁶, 3s², 3p⁴
• Xenon (Xe) (Z = 54): 1s², 2s², 2 P⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5 p⁶
• Lead (Pb) (Z = 82): 1s², 2s², 2 P⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5 p⁶, 6s², 4f¹⁴, 5 d¹⁰, 6p²
• Argon (Ar) (Z = 18): 1s², 2s², 2 P⁶, 3s², 3p⁶
• Cobalt (Co) (Z = 27): 1s², 2s², 2 P⁶, 3s², 3p⁶, 4s², 3d⁷