Related Directory Categories
- By Time Period (5790)
- Twentieth Century (2846)
- Wars and Conflicts (2016)
- Ancient (1238)
- World War II (1050)
- Nineteenth Century (669)
- Middle Ages (545)
- Periods and Cultures (490)
- World War I (471)
- Rome (458)
Sources
Help build the largest human-edited directory on the web.
Submit a site - Become an editor
Wikipedia. Licensed under the GNU Free Documentation License.
Are you an expert in this subject? Join the discussion and share your knowledge at Wikipedia.org.
Period (periodic table)
From Wikipedia, the free encyclopedia
In the periodic table of the elements, a period is a horizontal row of the table.
The elements are laid out in a series rows so that those with similar properties line up in horizontal columns: this reflects the periodic recurrence of similar properties as the atomic weight increases.
Modern quantum mechanics explains these periodic trends in properties in terms of electron shells. As atomic number increases, electron shells are filled in roughly this order. The filling of each shell corresponds to a row in the table.
1s
2s 2p
3s 3p
4s 3d 4p
5s 4d 5p
6s 4f 5d 6p
7s 5f 6d 7p
6f 7d 7f
...
Hence the structure of the periodic table. Since the valence electrons determine chemical properties, those tend to be similar within periodic table groups.
Elements adjacent to one another within a group have similar physical properties, despite their significant differences in mass. Elements adjacent to one another within a period have similar mass but different properties.
|
|
|
|---|---|
| Layouts | Standard · Vertical · Full names · Names and atomic masses · Text for last · Huge table · Metals and nonmetals · Blocks · Valences · Inline f-block · 218 elements · Electron configurations · Atomic masses · Electronegativities · 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 |
| Element categories | Alkalis · Alkaline earths · Lanthanides · Actinides · Transition metals · Metals · Metalloids · Nonmetals · Halogens · Noble gases |
| Blocks | s-block · p-block · d-block · f-block · g-block |