can't set values for checkbox attributes in jquery

I have group of checkbox in a table as,

 <input type="checkbox" id1='2' id2="" id3=""/>

gave a default value for id1 and initially value set as empty for id2 and id3. Is this right?? On a button action I am looping all these check boxes as,

                   $("input:checkbox").each(function(){
                         var $this = $(this);

                    });

In this action I have to assign values for id2 and id3(as empty before). I tried many ways, but nothing worked. Can anyone help??