), NON-METALS ( ) and METALLOIDS ( ). reactive metals with low ionization enthalpies. They lose the outermost electron(s) readily to form + ion (in the case of alkali metals) or + ion (in the case of alkaline earth metals). The metallic character and the reactivity increase as we go down the group.
Because of high reactivity they are never found pure in nature. The compounds of the s- block elements, with the exception of those of lithium and beryllium are predominantly ionic. . .
The p- Block Elements The p -Block Elements comprise those belonging to Group to and these together with the s- Block Elements are called the Representative Elements or Main Group Elements . The outermost electronic configuration varies from ns np to ns np in each period. At the end of each period is a noble gas element with a closed valence shell ns np configuration. All the orbitals in the valence shell of the noble gases are completely filled by electrons and it is very difficult to alter this stable arrangement by the addition or removal of electrons.
The noble gases thus exhibit very low chemical reactivity. Preceding the noble gas family are two chemically important groups of non- metals. They are the halogens (Group ) and the chalcogens (Group ). These two groups of elements have highly negative electron gain enthalpies and readily add one or two electrons respectively to attain the stable noble gas configuration.
The non-metallic character increases as we move from left to right across a period and metallic character increases as we go down the group. . . The d- Block Elements (Transition Elements) These are the elements of Group to in the centre of the Periodic Table.
These are characterised by the filling of inner d orbitals by electrons and are therefore referred to as d- Block Elements . These elements have the general outer electronic configuration ( n- ) d - ns - except for Pd where its electronic configuration is 4d 5s . . They are all