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the Elektronenkonfiguration gives the distribution of the bonding electrons of an atom on different energy conditions and/or. Lounges (orbital) on.

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the quantum numbers

the principal quantum number< math> n< /math> determines the main energy level, the bowl in such a way specified, and the relativeSize of the Orbitals. The outermost bowl occupied by electrons determines the period of the element in the periodic system. The bowls are durchnummeriert of 1 beginning or with the letters K, L, M, N… designated. The maximum number of electrons into thatindividual bowls results from the formula <math> 2 \ cdot n^2< /math>. Theoretically arise thus for the individual bowls:

  • K-bowl (n=1) = 2 electrons
  • L-bowl (n=2) = 8 electrons
  • M-bowl (n=3) = 18 electrons
  • N-bowl (n=4) = 32 electrons
  • O-bowl (n=5) =Math l

/math ,<> the angular momentum<,> the bowl divides 50 electrons the angular momentum quantum number into lower shells of different energy levels. The bowl <math> n< /math> exactly math <n> /math< possesses> Lower shells, nummeriert from <math> 0< /math> to <math> (n-1)< /math> or with the letters s, p, D, f, g, h… designated. Likewise becomesthe shape of the individual orbital through <math> l< /math> determined. Like the name arises out math l </math> already< says> the angular momentum of the respective Orbitals

the magnetic angular momentum quantum number< math> m< /math> the orientation of the Orbitals indicates in the area. In addition math <m> /math< makes> a statement overthe behavior of the respective Orbitals in a magnetic field and divides each lower shell into <math> 2l + 1< /math> Orbital one, nummeriert from <math> - l< /math> to <math> +l< /math>. Thus e.g. arises. for the p-orbital 3 partitionings: <math> p_x< /math>, <math> p_y< /math> and <math> p_z< /math>. Everyone these can of 2Electrons antiparallel spins to be occupied (see Pauli-Prinzip and Hund rule)

by these 3 quantum numbers an orbital is characterized. <math> n, l, m< /math> point out us, which orbital is occupied by the electron, e.g. <math> n=2< /math>, <math> l=1< /math> it shows that the electron in the 2.Flat one is taken up in an p-orbital (<math> l=0 \ rightarrow< /math> s; <math> l=1 \ rightarrow< /math> p; <math> l=2 \ rightarrow< /math> D, etc.) through <math> m< /math> now it is still characterized whether <math> p_x< /math>, <math> p_y< /math> or <math> p_z< /math> - orbital of the electron is occupied.

The electron becomesby 4 quantum numbers clearly characterizes. One must consider for this that electrons can rotate around their own axle, with or against the clockwise direction. The self-rotation of the electrons described by the spin quantum number< math> s< /math>. <math> s = +< /math> ½ (↑, spin UP) or <math> s =-< /math> ½ (↓, spindown).

Elektronenkonfiguration eines Sauerstoffatoms im Kästchenschema
Elektronenkonfiguration of an oxygen atom in the small box pattern


the Elektronenkonfiguration of an atom is described by indicating the occupied lower shells. Thereby the letter for the lower shell follows the number of the bowl and put up the number of electronsin the bowl. Thus arises for with 5 the electrons occupied 2. Lower shell of the 2. The flat way of writing 2p 5. With several lower shells the common bowl is omitted. From 2s 2 2p 3 2s 2 p 3 becomes. One receives a further shortened way of writing, if one sets the contraction for the preceeding noble gas into square brackets and indicates then the lower shells, which are missing still to the desired element. This is used because of its shortness in the periodic system: Example: Chlorine:1s 2 2s 2 2p 6 3s 2 3p 5 -> [Ne] 3s 2 3p 5 Besides still the descriptive diagram the cell way of writing (small box pattern) is usual.


with the distribution of the electrons in the atomic shell must different rules to be considered:

Energy principle: Orbital ones with lower energy level must be first filled up.

Hund rules: Orbital ones same energy levels are simply occupied first all, before they are occupied doubly.

Pauli-Prinzip (also Pauli prohibition): It may not do two electrons with agreeingQuantum numbers give. I.e. If 2 electrons already agree in n, l, and m and thus and occupied the same orbital, they must exhibit different values in the fourth quantum number s (spin quantum number). Thus arise occupied orbital alsoantiparallel (electron) spin.

The lower shells are occupied in the following order (line by line arranged):

1s (1. Period) 2s 2p (2. Period) 3s 3p (3. Period) 4s 3d 4p (4. Period) 5s 4d 5p (5. Period) 6s 4f 5d 6p (6. Period) 7s 5f6d… (7. Period)

of the rules specified above gives it several exceptions, among other things:

  • With lanthans occupied first an electron an orbital of the 5d-Unterschale before 4f is filled up, with actinium occupied according to an electron 6d before 5f is filled up.The electrons occupy first empty orbital within a lower shell.
  • With copper and chrome an electron of the 4s of Orbitals changes into the 3d orbital, so that the 4s orbital is only simply occupied despite its lower energy level.
  • Further exceptions are: Nb, Mo,Tc, Ru, RH, RD, AG, IR, Pt, outer one, Gd and some Actinoide: AC to NP and cm.

connection with the periodic system

in the periodic system corresponds the occupation of the s-Orbitals to a new bowl, the jump into a new period(see order of the electron population). Within one period first the s-orbital (2 electrons becomes - 1. and 2. Main group) and as the last p-orbital (6 electrons - 3. to 8. Main group) occupies. The Nebengruppen corresponds to occupying the D-orbital (10 electrons- 10 Nebengruppen). The Lanthanoide and Actinoide correspond to the occupation of the f-orbital (14 electrons).

see also

drillingSommerfeld atom model

to sources

  • Erwin Riedel, inorganic chemistry, 2. Edition, 1990 (for the exceptions of the rule for occupationthe atomic orbital)

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