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IE1- . Metals Metalloids Non Metal Radio active Group No Figure . p-block elements with their ionisation enthalpies, electronegativity and metallic nature. - - - - In p-block, the elements present in lower left part are metals while the elements in the upper right part are non metals.
Elements of group have metallic character except the first element boron which is a metalloid, having properties intermediate between the metal and nonmetals. The atomic radius of boron is very small and it has relatively high nuclear charge and these properties are responsible for its nonmetallic character. In the subsequent groups the non-metallic character increases. In group elements, carbon is a nonmetal while silicon and germanium are metalloids.
In group , nitrogen and phosphorus are non metals and arsenic & antimony are metalloids. In group , oxygen, sulphur and selenium are non metals and tellurium is a metalloid. All the elements of group and are non metals. .
. Ionisation Enthalpy: We have already learnt that as we move down a group, generally there is a steady decrease in ionisation enthalpy of elements due to increase in their atomic radius. In p-block elements, there are some minor deviations to this general trend. In group , from boron to aluminium the ionisation enthalpy decreases as expected.
But from aluminium to thallium there is only a marginal difference. This is due to the presence of inner d and f-electrons which has poor shielding effect compared to s and p-electrons. As a result, the