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
group | 1 | 18th |
|
I. | VIII |
Atomic number symbol |
1 H. |
2 He |
other non-metals | Noble gas |
Common characteristics
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
Magic number
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 |
list
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 |