Periodic table blocks are sets of elements grouped by their valence electron orbitals. The four block names are s-block, p-block, d-block, and f-block. Should a new element be discovered, it will be in g-block. Each block indicates which electron sublevel is in the process of being filled.
Charles Janet introduced the concept of element blocks as an alternative to element groups (and also envisaged helix and left-step periodic tables).
Periodic Table Block Names
The block names come from the electron azimuthal quantum number values, which represent characteristics of spectroscopic lines: sharp (0), principal (1), diffuse (2), or fundamental (3). G-block gets its name because “g” is the next letter after “f”.
The four periodic table blocks are the basis for the main group (s- and p-blocks), transition metal (d-block), and inner transition metal (f-block) elements.
Properties of Periodic Table Blocks
The s-block elements (except for helium) are on the left side of the periodic table.
- With the exception of helium (and possibly hydrogen), all of the s-block elements are metals. The s-block includes the alkali metals and alkaline earth metals.
- S-block elements tend to form soft solids with low melting points.
- With the exception of helium, all s-block elements are electropositive and reactive.
The p-block elements are on the right side of the periodic table. They include the last six element groups of the table (except for helium). P-block elements include all of the nonmetals (except hydrogen and helium), all of the metalloids, and the post-transition metals.
- P-block elements can gain, lose, or share their valence electrons.
- Most p-block elements form covalent compounds. The halogens form ionic compounds with s-block elements.
D-block elements are the transition metals (groups 3-12).
- D-block elements display properties between those of the highly reactive electropositive s-block elements and the more electronegative p-block elements. This is why they are called “transition” metals.
- These elements are all metals, usually with two or more oxidation states.
- D-block elements tend to have high melting points and boiling points.
- Many of these elements form colored complexes and salts.
- D-block elements tend to be good catalysts.
- F-block elements display variable oxidation states.
- Most f-block elements have high melting points.
- These elements form colored complexes and salts, but they tend to be paler than those formed by d-block elements.
- Many of the f-block elements (the actinides) are radioactive.
The g-block elements will be elements beyond oganesson (element 118). As these elements have not yet been synthesized, their properties have yet to be determined.
Blocks vs Groups and Periods
Blocks, groups, and periods are three broad ways of classifying elements based on their position on the periodic table and common properties.
- Blocks indicate which electron sublevel is being filled.
- Groups are the vertical columns on the periodic table. Moving down a group adds a new electron subshell. For s-block elements, the group number is the number of valence electrons. for p-block elements, the group number is 10 plus the number of valence electrons. For d-block elements, the group numbers is (n-1) the number of electrons in the subshell plus the number of electrons in the valence shell.
- Periods are the horizontal rows of the periodic table. The length of a period is determined by the number of electrons needed to fill the electron sublevel.
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- Stewart, Philip (April 2010). “Charles Janet: Unrecognized Genius of the Periodic System”. Foundations of Chemistry. 12: 5–15. doi:10.1007/s10698-008-9062-5