Write down the proper HTML5 code to display the following: H_(2)O Answer: square

To display the chemical formula $H_{2}O$ in HTML5, you can use the `<sup>` tag for the subscript and the `<sub>` tag for the subscript. Here is the proper HTML5 code:<br /><br />```html<br /><p>H<sub>2</sub>O</p><br />```<br /><br />In this code, the `<sub>` tag is used to display the subscript "2" for the hydrogen atom, and the `<sup>` tag is used to display the subscript "O" for the oxygen atom. The text is enclosed within a `<p>` tag to display it as a paragraph.