In chemistry, the representative elements are the elements with atoms filling s and p electron orbitals. Another name for the representative elements is the main group elements. The representative elements are groups 1 and 2 and group 13-17 on the periodic table. The outer electron shell is not filled for these elements, giving them a valence electron configuration of ns1-2 (s-block elements) and np1-5 (p-block elements). Some sources also include group 18.
Are the Noble Gases Representative Elements?
Whether or not the noble gases or group 18 elements are representative elements depends on who you ask. On the one hand, they are s– and p-block elements. On the other hand, they have filled valence shells and are not very reactive.
Why Are They Called Representative Elements?
Representative elements get their name because each element shares or represents the properties of other elements in its group. An element in a periodic table group shares the same number of valence electrons and electron configuration as other elements in the group. For example, lithium and sodium are both elements in group 1 (the alkali metals) and have 1 valence electron and similar properties. In contrast, valence and electron configuration gets less clear-cut with the transition metals, lanthanides, and actinides (d– and f-block elements).
Examples of Representative Elements
Elements belonging to groups 1, 2, 13-17 are representative elements Elements belonging to group 3-16 (and 18, usually) are not representative elements. In other words, the transition metals, lanthanides, actinides, and (usually) noble gases are not representative elements.
For example, lithium, sodium, and potassium are representative of group 1. Beryllium and strontium are representative of group 2. Carbon and silicon are representative of group 14. Hydrogen, magnesium, gallium, and iodine are all representative elements. Titanium, iron, and uranium are not representative elements.
S-Block and P-Block Properties
The properties of the representative elements depends on whether they are s-block or p-block elements. Overall, the s-block elements are most like each other than the p-block elements.
S-Block Properties
- S-block elements have a single oxidation state. For group 1 (alkali metals) this is +1. For group 2 (alkaline earths) this is +2. Of course, there are exception. For example, hydrogen usually takes a +1 oxidation state, but sometimes has a -1 oxidation state.
- S-block elements are highly reactive. Helium is the exception here, but it isn’t normally considered to be a representative element.
- These elements are soft reactive metals (again, except helium), with low melting and boiling points.
P-Block Properties
- P-block elements typically display multiple oxidation states, favoring states separated by two units. For example, the oxidation states of sulfur are -2, 0, +2, +4, +6 (where the bold states are more common).
- This collection of elements includes nonmetals, metalloids, and metals. However, elements within a group still share some common properties.
Importance of the Representative Elements
The representative elements include the majority of the most abundant elements on Earth and in the universe. Similarly, they include many of the elements essential to organic molecules and life. Most commercial projects are rich in these elements.
References
- 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
- Steudel, Ralf (1998). Chemie der Nichtmetalle (Chemistry of the Nonmetals) (2nd ed.). Berlin: Walter deGruyter. ISBN 3-11-012322-3.
- Yao, Benzhen; Kuznetsov, Vladimir L.; et al. (2020). “Metals and non-metals in the periodic table”. Philosophical Transactions of the Royal Society A. 378. doi:10.1098/rsta.2020.0213