User:Edgar181/query

SELECT DISTINCT ?item ?itemLabel WHERE 
{
  ?item wdt:P31 wd:Q11173. 
  ?article_de schema:about ?item ;
          schema:isPartOf <https://de.wikipedia.org/> .
filter not exists {  
  ?article_en schema:about ?item ;
          schema:isPartOf <https://en.wikipedia.org/> . }
  SERVICE wikibase:label { bd:serviceParam wikibase:language "en,de" . }    
}

Try it!

SELECT ?chem {
  ?chem wdt:P31 wd:Q11173 .
  OPTIONAL {
    ?chem rdfs:label ?chemLabel.
    FILTER(LANG(?chemLabel) = "en") .
  }
  FILTER(!BOUND(?chemLabel)) .
}

Try it!