Period 1 element
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A period 1 element is one of the chemical elements in the first row (or period) of the periodic table of the elements.
Period one is much shorter than any other row in the table, and contains only two elements, hydrogen and helium. In a quantum mechanical description of atomic structure, this period corresponds to the filling of the the 1s orbital. Period 1 elements do not obey the "octet rule".
These are:
| Group | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| # Name |
1 H |
2 He |
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| e--conf. | ||||||||||||||||||
| Alkali metals | Alkaline earth metals | Lanthanides | Actinides | Transition metals |
| Poor metals | Metalloids | Nonmetals | Halogens | Noble gases |
Standard · Vertical · Full names · Names and atomic masses · Text for last · Huge table · Atomic masses
Electron configurations · Metals and nonmetals · Blocks · Valences · Inline f-block · 218 elements · Alternatives
Lists of elements:
Name · Atomic symbol · Atomic number · Boiling point · Melting point · Density · Atomic mass
Groups:
1 · 2 · 3 · 4 · 5 · 6 · 7 · 8 · 9 · 10 · 11 · 12 · 13 · 14 · 15 · 16 · 17 · 18
Periods:
1 · 2 · 3 · 4 · 5 · 6 · 7 · 8
Series:
Alkalis · Alkaline earths · Lanthanides · Actinides · Transition metals
Poor metals · Metalloids · Nonmetals · Halogens · Noble gases
