Editing Period 5 element (section)

=== Rubidium ===
{{main|Rubidium}}

'''Rubidium''' is the first element placed in period 5. It is an [[alkali metal]], the most reactive group in the [[periodic table]], having properties and similarities with both other alkali metals and other period 5 elements. For example, rubidium has 5 electron shells, a property found in all other period 5 elements, whereas its [[electron configuration]]'s ending is similar to all other alkali metals: s<sup>1</sup>.<ref>{{cite web|url=http://environmentalchemistry.com/yogi/periodic/Rb.html |title=Periodic Table of Elements: Rubidium – Rb |publisher=EnvironmentalChemistry.com |date=1995-10-22 |access-date=2012-08-13}}</ref> [[Rubidium]] also follows the trend of increasing [[reactivity (chemistry)|reactivity]] as the atomic number increases in the alkali metals, for it is more reactive than [[potassium]], but less so than [[caesium]]. In addition, both potassium and rubidium yield almost the same hue when [[wikt:ignition|ignited]], so researchers must use different methods to differentiate between these two 1st group elements.<ref>{{cite web|url=http://webmineral.com/help/FlameTest.shtml |title=Flame Tests |publisher=Webmineral.com |access-date=2012-08-13}}</ref> Rubidium is very susceptible to [[Redox|oxidation]] in air, similar to most of the other alkali metals, so it readily transforms into [[rubidium oxide]], a yellow solid with the [[chemical formula]] Rb<sub>2</sub>O.<ref>{{cite web|url=http://www.chemguide.co.uk/inorganic/group1/reacto2.html |title=Reactions of the Group 1 elements with oxygen and chlorine |publisher=Chemguide.co.uk |access-date=2012-08-13}}</ref>