16808
Abstraction of a hydrogen atom by a tertiary radical has a higher energy barrier than abstraction by a secondary radical , which agrees with experimental findings .
 Chemical: hydrogen
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: hydrogen 
Answer:
 Chemical: hydrogen