= <periodicelement> =

A '''{{{periodicelement}}}''' input element lets you choose an atomic element from a drop down table representing the periodic table.  The selection may be limited to specific atoms or groups of atoms.

[[rpimage(zoo_periodicelement.png)]]

== Example ==

{{{
  <periodicelement>
   <about>
    <label>Element</label>
    <description>Select the element.</description>
   </about>
   <default>H</default>
  </periodicelement>
}}}

You can limit the set of elements that can be selected.  The '''{{{<active>}}}''' and '''{{{<inactive>}}}''' sub-elements let you pick what elements can be selected. For example,

{{{
   <active>C O H</active>
}}}

allows only hydrogen, carbon, and oxygen atoms to be selected.  All other atoms are disabled.
Likewise, you can disable specific atoms.

{{{
   <inactive>Uut Uuq Uup Uuh</inactive>
}}}

You can turn on/off groups of atoms by specifying the group:

 ''actinoid''::
  Actinides Actinium Americium Berkelium Californium Curium 
  Einsteinium Fermium Mendelevium Neptunium Plutonium Protactinium 
  Thorium Uranium Lawrencium Nobelium	
 ''alkali-metal''::
  Cesium Francium Lithium Potassium Rubidium Sodium		
 ''alkaline-earth-metal''::
  Barium Beryllium Calcium Magnesium Radium Strontium	
 halogen::
  Astatine Bromine Chlorine Fluorine Iodine		
 ''lanthanoid''::
  Cerium Erbium Europium Gadolinium Holmium Lanthanides Lanthanum	
  Lutetium Neodymium Praseodymium Promethium Samarium Terbium 
  Thulium Ytterbium Dysprosium	
 ''metalloid''::
  Arsenic Boron Germanium Polonium Silicon Tellurium Antimony	
 ''noble-gas''::
  Argon Helium Krypton Neon Radon Xenon 
 ''other-non-metal''::
  Carbon Hydrogen Nitrogen Sulfur Oxygen Phosphorus Selenium	
 ''post-transition-metal''::
  Aluminium Bismuth Gallium Indium Lead Thallium Tin Ununhexium 
  Ununpentium Ununquadium Ununtrium	
 ''transition-metal''::
  Chromium Cobalt Copper Dubnium Gold Hafnium Hassium Iridium		
  Iron Manganese Meitnerium Mercury Molybdenum Nickel Niobium		
  Osmium Palladium Rhenium Rhodium Roentgenium Ruthenium 
  Rutherfordium Scandium Seaborgium Silver Tantalum Technetium 
  Titanium Tungsten Ununbium Vanadium Yttrium Zinc Zirconium 
  Bohrium Cadmium Darmstadtium Platinum	
 ''unknown''::
  Ununoctium	      Ununseptium	

{{{
   <inactive>transition-metal unknown post-transition-metal other-non-metal</inactive>
}}}

 == Value returned ==

The '''{{{<current>}}}''' value returned is normally the name of the atom selected (such as Carbon). You can specify what you would like to be returned by the '''{{{<returnvalue>}}}''' element.

{{{
   <returnvalue>number</returnvalue>
}}}

This says to return the atomic number of the element as the current value.  You can choose
one of the following:

 ''weight''::
   Returns the atomic weight of the element.
 ''number''::
   Returns the atomic number of the element.
 ''name''::
   Returns the name of the element. This is the default.
 ''symbol''::
   Returns the symbol of the element.
 ''all''::
   Returns a list of the name, number, symbol, and weight of the selected element.

 
== Tags == 

In the '''periodelement''', the following tags (sub-elements) are significant:

 '''{{{<about><label>}}}''':: 
 is the label displayed to the left of the entry showing the current element.
 '''{{{<about><description>}}}'''::
 is a description displayed in a tool tip when the mouse pointer is over the input. This is used to provide a more detailed explanation of what this input represents.  
 '''{{{<active>}}}'''::
 is a list of element symbols or groups that indicate what elements are to be enabled for selection.  All other elements are disabled.
 '''{{{<default>}}}'''::
 is the default element to be selected in the entry.
 '''{{{<inactive>}}}'''::
 is a list of element symbols of groups that indicate what elements are to be disabled for selection.  All other elements are enabled.
 '''{{{<returnvalue>}}}'''::
 indicates what to return as the current value of this input. Valid values are ''name'', ''symbol'', ''number'', ''weight'', and ''all''.