Organization of the Periodic Table Based on Chemical Properties

What are the nine main groups of elements from left to right?

1. Alkali metals
2. Alkaline earth metals
3. Transition metals
4. Metalloids
5. Non-metals
6. Halogens
7. Noble gases
8. Lanthanides
9. Actinides

Figure 29.1: Periodic table: Nine main groups of elements: (1) Alkali metals, (2) alkaline earth metals, (3) transition metals, (4) metalloids, (5) non-metals, (6) halogens, (7) noble gases, (8) lanthanides, and (9) actinides.

What are some notable chemical characteristics of the following groups?

1. Alkali metals (Group 1A)
   • Low densities, soft metals.
   • 1 valence $e^{-}$.
   • Oxidize very quickly: Potassium actually burns at STP.
2. Alkaline earth metals (Group 2A)
   • 2 valence $e^{-}$.
   • Also oxidize quickly.
3. Transition metals
   • Hard metals with high melting point and high boiling points.
   • Relatively loose hold on valence shell electrons allows for electrical conductivity.
   • Compared to Groups 1A and 2A, transition metals oxidize slower (if at all), e.g. Ag tarnishes over months, iron also oxidizes over time (rusts), but Au does not oxidize easily.
4. Metalloids
   • These elements pull away from the classic metals like Cu or Al, but still share metallic and non-metallic properties. For example, Si is a semiconductor of electrical current (a metallic property), while it also is capable of transmitting light (a non-metallic property).
5. Non-metals
   • Wide range of chemical properties and ability to react with other atoms. Just think of C or O, they can react with many types of atoms.
6. Halogens (Group 7A)
   • Highly reactive non-metals which exist in different forms at room temperature, e.g. F$_{2}$ is a gas while I$_{2}$ is a solid.
7. Noble gases (Group 8A)
   • These are inert gases with a full complement of valence of electrons.
   • Respective noble gases are used for shorthand notation of electronic configurations.
8. Lanthanides and actinides
   • These elements are included in this review for the sake of completeness. Also known as rare earth elements, lanthanides and actinides have partly-filled f orbitals with empty outermost p and d orbitals (see Figure below). Additionally, lanthanides and actinides have radioactive elements and some have very short half-lives.

     Figure 29.2: Extended periodic table: Note that lanthanides (8) and actinides (9) have empty p and d orbitals.

     

What are the representative elements?

The representative elements are the elements in the s and p blocks, i.e.  groups 1A, 2A, 3A, 4A, 5A, 6A, 7A and 8A. See Figure 29.3 below.

Figure 29.3: Periodic table: The representative elements - Elements in the s and p blocks.