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: Ninety - five percent of patients in each group who attained a score of 5 at the 5 - minute assessment showed no loss of alertness throughout the 180 - minute assessment period .
### Output Text:
Ninety - five percent of patients in each group who attained a score of 5 at the 5 - minute assessment showed no loss of alertness throughout the 180 - minute assessment period . 