In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: The case illustrates that , despite the results of earlier studies , trazodone ' s effect on cardiac conduction may be severe in individuals at risk for conduction delay .
### Output Text:
The case illustrates that , despite the results of earlier studies , <span class="chemical">trazodone</span> ' s effect on cardiac conduction may be severe in individuals at risk for conduction delay . 