The Periodic Table as Musical Notes
Copyright © 2009 by the Phoenix Foundation. All rights reserved.

Copyright © 2009 by the Phoenix Foundation. All rights reserved.

Standard periodic table

This common arrangement of the periodic table separates the lanthanides and actinides from other elements. The wide periodic table incorporates the f-block. The extended periodic table adds the 8th and 9th periods, incorporating the f-block and adding the theoretical g-block.

Noble Gases
Main article: noble gas

All the elements of Group 18, the noble gases, have full valence shells. This means they do not need to react with other elements to attain a full shell, and are therefore much less reactive than other groups. Neon followed by helium are the most inert elements among noble gases, since reactivity, in this group, increases with the periods: it is possible to make heavy noble gases react since they have much larger electron shells. However, their reactivity remains very low in absolute terms.

Halogens (Active Gases)
Main article: halogen

In Group 17, known as the halogens, elements are missing just one electron each to fill their shells. Therefore, in chemical reactions they tend to acquire electrons (the tendency to acquire electrons is called electronegativity). This property is most evident for fluorine (the most electronegative element of the whole table), and it diminishes with increasing period.

As a result, all halogens form acids with hydrogen, such as hydrofluoric acid, hydrochloric acid, hydrobromic acid and hydroiodic acid, all in the form HX. Their acidity increases with higher period, for example, with regard to iodine and fluorine, since a large I⁻ ion is more stable in solution than a small F⁻, there is less volume in which to disperse the charge.

Lanthanoids and actinoids
Main articles: lanthanoid and actinoid

The chemical properties of the lanthanoids (elements 57–71) and the actinoids (elements 89–103) are even more similar to each other than the transition metals, and separating a mixture of these can be very difficult. This is important in the chemical purification of uranium concerning nuclear power.

Lanthanoids

All lanthanoids closely resemble lanthanum. They are electropositive trivalent metals. They are shiny and silvery-white, and tarnish easily when exposed to air. They react violently with most nonmetals. They are relatively soft but their hardness increases with their atomic number. Lanthanoids burn in air. They have high melting and boiling points.

Actinoids

The actinoids display less similarity in their chemical properties than the lanthanoid series (Ln), exhibiting a wider range of oxidation states, which initially led to confusion as to whether actinium, thorium, and uranium should be considered d-block elements. All actinoids are radioactive.

Only thorium and uranium occur naturally in the Earth's crust in anything more than trace quantities. Neptunium and plutonium have been known to show up naturally in trace amounts in uranium ores as a result of decay or bombardment. The remaining actinoids were discovered in nuclear fallout, or were synthesized in particle colliders. The latter half of the series possess exceedingly short half-lives.