Period of the periodic table

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In chemistry, a period of the periodic table is understood to mean every line of the periodic table of the elements . The period numbers 1 to 7 correspond to the main quantum numbers , the period letters K to Q, which are often indicated, correspond to the shells of the shell model of the atomic shell .

Except for the first period, which only contains the elements hydrogen and helium, each period comprises eight main group elements. From the 4th period (inclusive) ten subgroup elements are added. The 6th period also contains 14  lanthanoids , the 7th period 14  actinides :

period Electrons elements Remarks
-Bowl -orbital /
s block p block d block f block g block
1 K s 2
2 L. s, p 2 6th
3 M. s, p 2 6th
4th N s, p, d 2 6th 10
5 O s, p, d 2 6th 10
6th P s, p, d, f 2 6th 10 14 1
7th Q s, p, d, f 2 6th 10 14 2
8th s, p, d, f, g 2 6th 10 14 3 18 3 no element detected
1 Lanthanoids
2 Actinoids
3 Superactinoids

Rules and laws

Within a period, the atomic radii usually decrease from left to right and the electronegativity increases, as the number of positively charged protons in the atomic nucleus increases, and with it the number of negatively charged electrons in the atomic shell in a neutral atom . When using the shell model, the electron shells are filled up; when using a newer atomic model such as e.g. B. of the orbital model occupies the corresponding atomic orbitals .

The change in the number of atomic building blocks causes the different properties of the chemical elements within a period:

See also

Individual evidence

  1. ^ Wiberg, Egon., Wiberg, Nils ,: Textbook of Inorganic Chemistry . 102nd, heavily reworked and verb. Ed. De Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 .