For Bootstrap 3 the default radio/button-group structure is :
<div class="btn-group" data-toggle="buttons">
<label class="btn btn-primary">
<input type="radio" name="options" id="option1"> Option 1
</label>
<label class="btn btn-primary">
<input type="radio" name="options" id="option2"> Option 2
</label>
<label class="btn btn-primary">
<input type="radio" name="options" id="option3"> Option 3
</label>
</div>
And you can select the active one like this:
$('.btn-primary').on('click', function(){
alert($(this).find('input').attr('id'));
});