Thumbnail won't appear

Hello,

I need some help. The thumbnail won’t appear for this picture, and I can’t see the problem. I pasted the whole code just in case.

<div class="container">
  <div class="jumbotron">
  <div class="row">
    <div class="col-xs-12">
  <h1 class="text-center">Magnus Carlsen</h1>
    <h4 class="text-center"><i>Chess Grandmaster</i></h4>
   <div class="thumbnail"><img src="http://geeksnation.org/wp-content/forum/uploads/2016/11/Magnus-Carlsen.jpg";
      alt="Magnus Carlsen"; width="900"; height="500">
    <div class="caption text-center">Magnus Carlsen figuring out his next move</div>
      </div>
  <br>

       <h3>This is Carlsen's short bio:</h3>
  
      <ul>
        <li>List</li>
        <li>Yet another listy wist</li>
      </ul>
     
  </div>
</div>
 </div>
  </div>
<footer class="text-center">
  <hr>
  <p> Written and coded by Aron Geber</p>
</footer>

I cleaned up your code.
You need to use triple backticks to post code to the forum.
See this post for details.

Are you using codepen? If so, codepen defaults to Bootstrap 4.0.0-alpha. If you change it to the latest stable release (3.3.7), you should not have this problem (link below).

Also, you don’t have to use ; in your img src.