Non riesco a far partire un bottone

[Gioiello]

<script type="text/javascript">
var topic = "1"
$(document).ready(function(){
    $("#button_create").click(function() {
            alert('inside');
                        var postData = {
                            'topics' : topic,
                        };
                        $.ajax({
                            type: "POST" ,
                            dataType: "json" ,
                            url: base_url + "index.php/chat/create_new",
                            data: postData ,
                            success: function(data){
                                alert(data);
                            }
                        }); 
                        return false;
    });
</script>
<label for="topics"> <?php echo 'About: 1 '?></label>
<div id ="button_create">
<input type="button" value="Create">
</div>