Editing Period 4 element (section)

===Krypton===
[[File:Krypton discharge tube.jpg|frameless|left|upright=0.3]]
[[Krypton]] (Kr) is a [[noble gas]], placed under [[argon]] and over [[xenon]]. Being a noble gas, krypton rarely interacts with itself or other elements; although compounds have been detected, they are all unstable and decay rapidly, and as such, krypton is often used in fluorescent lights. Krypton, like most noble gases, is also used in lighting because of its many spectral lines and the aforementioned reasons.