The main group elements are the chemical elements belonging to the s-block and p-block on the periodic table. These are elements in group 1 and group 2 (s-block) and groups 13 through 18 (p-block). In older IUPAC group numbering systems, the main group elements are groups IA, IIA, and IIIA to VIIIA. When the periodic table is divided in this manner, the other main element categories are the transition metals and the inner transition metals.
The s-block elements are the alkali metals and alkaline earth metals. The p-block elements are the basic metals, metalloids, nonmetals, halogens, and noble gases. Examples of main group elements include helium, lithium, boron, carbon, nitrogen, oxygen, fluorine, and neon.
Elements that are not main group elements are the transition metals (such as titanium, copper, and gold), the lanthanides (such as lanthanum and erbium), and the actinides (such as actinium and plutonium). Some people don’t include the superheavy elements from meitnerium (atomic number 109) to oganesson (atomic number 118) because too few atoms have been synthesized to verify their properties and because these properties are heavily influenced by relativistic effects. Sometimes the element hydrogen (atomic number 1) is excluded as a main group element.
Other Main Group Elements
Some scientists believe the group 12 elements (zinc, cadmium, and mercury) should be included as main group elements because they share common properties with the elements to the right of them on the table. A few scientists include the group 3 elements (scandium and yttrium) and sometimes the lanthanides and actinides.
Main Group Element Properties
Main group element properties depend on whether they are s-block or p-block elements:
S-Block Element Properties
- The s-block elements have one oxidation state.
- Their general valence configuration is ns1–2.
- Group 1 elements (alkali metals) have a +1 oxidation state. Group 2 elements (alkaline earth metals) have a +2 oxidation state.
- With the exception of helium, all s-block elements are highly reactive.
- The s-block metals tend to be soft, with low melting and boiling points.
- S-block metals are highly electropositive. They form ionic compounds with nonmetals.
- Most of the s-block elements impart color to a flame.
P-Block Element Properties
- The p-block elements are characterized by having multiple oxidation states, often separated by two units. For example, the oxidation states of sulfur are -2, 0, +2, +4 and +6.
- But, oxidation state and other properties depend on the group. The group 17 elements (halogens) have an oxidation state of -1, while the group 18 elements (noble gases) have an oxidation state of 0.
- The general oxidation state of p-block metals is ns2 np1–6. Their valence electron is in the p orbital.
- P-block elements include nonmetals, metalloids, and metals, so their properties depend on their group.
Importance of the Main Group Elements
The main group elements are important for a few reasons:
- The main group elements, along with a few light transition metals, are the most abundant elements in the universe and on Earth. They comprise 80% of the Earth’s crust. For this reason, the main group elements are also called the representative elements.
- These elements are critical for supporting life. Biological molecules require main group elements, particularly carbon, oxygen, hydrogen, nitrogen, sulfur, and phosphorus.
- The main group elements and their compounds are among the most economically important elements. The majority of manufactured products contain these elements.
References
- IUPAC (2004). Nomenclature of Inorganic Chemistry.
- Jensen, William B. (2003). “The Place of Zinc, Cadmium, and Mercury in the Periodic Table”. Journal of Chemical Education. 80 (8): 952. doi:10.1021/ed080p952
- King, R. Bruce (1995). Inorganic Chemistry of Main Group Elements. Wiley-VCH. ISBN 0-471-18602-3.