Neeti
Last Activity: 9 Years ago
see, these are exceptions kind of. Li is in the second period and we know that second period elements show anomalous behaviour. you are right in saying that Mg has an extra shell but you should also consider the electronic configuration, position of the element etc. we know that second period elements are smaller than first period elements and 2 electrons are removed from Mg which actually makes it extra small, and smaller than Li.