Period of the periodic table
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 :
|s block||p block||d block||f block||g block|
|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|
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:
- the change in the number of building blocks in the atomic nucleus mainly causes the different physical properties
- the number and location of the electrons in the atomic shell mainly cause the different chemical properties.
- Wiberg, Egon., Wiberg, Nils ,: Textbook of Inorganic Chemistry . 102nd, heavily reworked and verb. Ed. De Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 .