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: Overall , 40 % of patients scored < 85 on either Verbal or Performance IQ .
### Output Text:
Overall , 40 % of patients scored < 85 on either Verbal or Performance IQ . 