i am quite sure that you can't add javascript directly into the html editor of a post.
to add google ads into a post or page, you could use shortcodes.
http://codex.wordpress.org/Shortcode_API
in functions.php of the theme, add:
// [adsense]
function add_adsense($atts) {
return '<span class="adsense">
<script type="text/javascript"><!--
google_ad_client = "pub-0123412341234123";
/* your google ads */
google_ad_slot = "1234512345";
google_ad_width = 468;
google_ad_height = 60;
//-->
</script>
<script type="text/javascript"
src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script>
</span>';
}
add_shortcode('adsense', 'add_adsense');
substitute your own google code.
the span with the class .adsense is optional to style the ads (for instance use float:left; with some margins to let the text float around the ads);
place them whereever you want in a post or page by typing [adsense] into the text.
you might also be able to find a plugin to deal with adsense.