Question

Choose the atom that matches the identified atomic property and explain your answer based on its position within a group or period in the periodic table: highest ionization Li , Be B

Answer 1

The elements are arranged according to their atomic number. Here, Li, Be, B having atomic number 3,4 and 5 respectively. This are present along a period , we know from left hand side to right hand side in a period the effective nuclear charge increases which results in decrease of their ionic radii .So, Li has larger radii than Be and B . We know with decreasing ionic radii it becomes difficult to ionize the electron of its outermost shell. So it our expectation that the first ionization energy of this three elements should be B>Be>Li, as their radii is in opposite order. But, in reality we observe some anomolies and the actual order is Be>B>Li. If we consider the electronic configuration then for Be the 2s orbital is completely filled(1s2 2s2) so, it's very much difficult to remove an electron from its filled 2s orbital. Though , here in Li 2s orbital is half filled(1s2 2s1) but as it is larger in size compared to B(1s2 2s2 2p1) so the order is above. So highest first ionisation energy follows by Be, where Li and B follow expected order.