17939
The surface polarity index was determined by XPS and expressed as ( oxygen + nitrogen ) - to - ( carbon ) atomic concentration ratio .
 Chemical: oxygen; Chemical: nitrogen; Chemical: carbon
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: oxygen; Chemical: nitrogen; Chemical: carbon