<input id="check_1" name="check[1]" type="checkbox" value="1"/>
<label for="check_1">One</label>&nbsp;

<input id="check_2" name="check[2]" type="checkbox" value="1"/>
<label for="check_2">Two</label>&nbsp;

<input id="check_3" name="check[3]" type="checkbox" value="1"/>
<label for="check_3">Three</label>

$("#check_1").change(function() {
  alert('Checkbox One is clicked');
});