Group
Definition and meaning of Group in chemistry.
A group is a vertical column of elements in the periodic table, numbered 1 through 18, whose members share the same number of valence electrons and therefore display similar chemical behavior.
In more detail
Because elements in a group have the same outer-shell electron configuration, they tend to form similar types of ions and compounds and undergo analogous reactions. Properties still shift gradually down a group as atomic radius increases and ionization energy generally decreases, due to additional electron shells and increased shielding. Many groups have traditional family names, such as the alkali metals, alkaline earth metals, halogens, and noble gases, reflecting their shared reactivity patterns.
Key facts
| Field | General Chemistry |
|---|---|
| Total groups | 18 (IUPAC numbering) |
| Also called | Family |
| Key trend | Same valence electron count down a column |
Group 1 (the alkali metals: Li, Na, K, Rb, Cs, Fr) all have one valence electron and readily lose it to form +1 cations, making them highly reactive metals that react vigorously with water.
Frequently asked questions
What is the difference between a group and a period?
A group is a vertical column (elements share valence electron count and similar properties); a period is a horizontal row (elements share the same number of electron shells).
Why do elements in the same group behave similarly?
They have the same number of valence electrons, which primarily determines an element's bonding behavior and typical ion charge.