What Are Element Blocks?

Element blocks are different from periods or groups

Blocks include elements of adjacent groups.
Blocks include elements of adjacent groups. Todd Helmenstine

One way to group elements is by element blocks, sometimes known as element families. Element blocks are distinct from periods and groups because they were developed based on a very different way of categorizing atoms.

What Is an Element Block?

An element block is a set of elements located in adjacent element groups. Charles Janet first applied the term (in French). The block names (s, p, d, f) originated from descriptions of spectroscopic lines of atomic orbitals: sharp, principal, diffuse and fundamental.

 No g block elements have been observed to date, but the letter was chosen because it is next in alphabetical order after 'f'.

Which Elements Fall Into Which Block?

Element blocks are named for their characteristic orbital, which is determined by the highest energy electrons:

s-block
The first two groups of the periodic table, the s-block metals:

  • are either alkali metals or alkaline earth metals
  • are soft and have low melting points
  • are electropositive and chemically active

p-block
P-block elements include the last six element groups of the periodic table, excluding helium. The p-block elements include all of the nonmetals except for hydrogen and helium, the semimetals, and the post-transition metals. P-block elements:

  • include carbon, nitrogen, oxygen, sulfur, halogens, and many other common elements
  • interact with other chemicals by losing, gaining or sharing the valence electrons. 
  • mostly form covalent compounds (though the halogens form ionic compounds withs-block metals.

    d-block

    D-block elements are transition metals of element groups 3-12. D-Block elements:

    • have valence electrons in their two outermost and shells
    • 'd' block elements behave in a manner that is somewhere between that of highly reactive electropositive alkali metals and the covalent compound forming elements (which is why they are called "transition elements").
      • have high melting and boiling points 
      • usually form colored salts.
      • are generally good catalysts.

      f-block
      Inner transition elements, usually the lanthanide and actinide series, including lanthanum and actinium. These elements are metals which have:

      • high melting points
      • variable oxidations states
      • the ability to form colored salts

      g-block (proposed)

      Would be expected to include elements with atomic numbers higher than 118.

       

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      Helmenstine, Anne Marie, Ph.D. "What Are Element Blocks?" ThoughtCo, Jan. 5, 2018, thoughtco.com/periodic-table-element-blocks-608788. Helmenstine, Anne Marie, Ph.D. (2018, January 5). What Are Element Blocks? Retrieved from https://www.thoughtco.com/periodic-table-element-blocks-608788 Helmenstine, Anne Marie, Ph.D. "What Are Element Blocks?" ThoughtCo. https://www.thoughtco.com/periodic-table-element-blocks-608788 (accessed January 18, 2018).