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: 7e exhibits a high reversal of catalepsy induced by haloperidol indicating its atypical antipsychotic nature .
### Output Text:
7e exhibits a high reversal of catalepsy induced by <span class="chemical">haloperidol</span> indicating its atypical antipsychotic nature . 