"Estrontium" on poster
"Estrontium" is not used as an element name in any language. It appears that the error traces to a single user by the name of Alejo Miranda (listed as from Ecuador) who has posted a large collection of periodic tables and individual element clip art to shuttersock, iphoto, etc. in which "estrontium" is incorrectly used as the English name for strontium.  The Spanish periodic table correctly uses estroncio.  The link to the gllery at shutterstock is 

https://www.shutterstock.com/g/Alejo+Miranda?searchterm=estrontium&amp;search_source=base_gallery&amp;language=en&amp;sort=popular&amp;measurement=px&amp;safe=true