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: Cross - sectional echocardiographic screening of newborns exposed to lithium during gestation can provide highly accurate , noninvasive assessment of the presence or absence of lithium - induced cardiac malformations .
### Output Text:
Cross - sectional echocardiographic screening of newborns exposed to <span class="chemical">lithium</span> during gestation can provide highly accurate , noninvasive assessment of the presence or absence of <span class="chemical">lithium</span> - induced cardiac malformations . 