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: An 11 - year - old boy was given halothane , nitrous oxide and oxygen , pancuronium 0 . 4 mg and suxamethonium 100 mg for induction of anaesthesia .
### Output Text:
An 11 - year - old boy was given <span class="chemical">halothane</span> , <span class="chemical">nitrous oxide</span> and <span class="chemical">oxygen</span> , <span class="chemical">pancuronium</span> 0 . 4 mg and <span class="chemical">suxamethonium</span> 100 mg for induction of anaesthesia . 