Chemical elements of the first period
The first period of the periodic table of the elements includes all chemical elements that have only one electron shell in the atom . This electron shell is also called the valence shell of the atom. Since this first electron shell can only hold a maximum of two electrons , there are only two chemical elements in the first period. The valence shell, which largely determines the properties of a chemical element, is already fully occupied with 2 electrons in elements of the 1st period. In all other periods the valence shell is only fully occupied from 8 electrons.
Extract from the periodic table
|other non-metals||Noble gas|
Both chemical elements of the first period are gaseous under standard conditions , are colorless gases and have diamagnetic properties.
- The gases
Hydrogen in a discharge tube
Helium in a discharge tube
The chemical element helium with atomic number two has a higher stability in the basic state of the atomic nucleus than neighboring nuclides . This particular ordinal number is known as the magic number .
Number of electrons in the electron shells
|Electron shell||Number of electrons||comment|
|All in all||s orbital||p orbital||d orbital||f orbital|
|1||1 to 2||1 to 2||-||-||-||outermost electron shell , valence shell|
|Atomic number||symbol||Surname||Element category||Physical state||Electron configuration|
|1||H||hydrogen||other non-metals||gaseous||1s 1|
|2||Hey||helium||Noble gases||gaseous||1s 2|