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: Corresponding figures for whole body K were 4107 + / - 208 , 3722 + / - 319 , 3628 + / - 257 , 3551 + / - 336 , and 3269 + / - 380 mEq , respectively .
### Output Text:
Corresponding figures for whole body <span class="chemical">K</span> were 4107 + / - 208 , 3722 + / - 319 , 3628 + / - 257 , 3551 + / - 336 , and 3269 + / - 380 mEq , respectively . 