State all the exceptions to the general trend of metallic and non metallic character with reasons.


The metallic character is the ability to lose electrons while the non-metallic character is the ability to accept electrons. Based on this theory, the general trend of metallic & non-metallic characters is as follows-
  • The metallic character decreases across the period while the non-metallic character increases. As we move across a period, the atomic radius decreases. Reasons-
    • The electrons are more tightly bound to the nucleus. So, ionization energy also increases, that is the energy needed to remove an electron from the outermost shell. So, while moving across the period, the ability to lose electrons also decreases, and thus metallic character decreases.
    • Across a period the atomic number of the elements increases but the shell number remains the same. Due to this, the nuclear attraction is more. Since the nucleus has positively charged protons, it attracts the electrons. Hence the tendency to accept electrons increases. Since the tendency to gain electrons is a non-metallic characteristic, hence non-metallic character increases across a period. 
  • The trend down a group is that the metallic character increases down the group while the non-metallic character decreases. Reasons-
    • The metallic character increases as you move down the group in the periodic table. This is because electrons become easier to lose as the atomic radius increases, where there is less attraction between the nucleus and the valence electrons because of the increased distance between them.
    • If we move down the group, the electron affinity of the species will be decreased but the size of the substances will be increased. The non-metallic character is dependent on the electron affinity of the atom. Hence, the non-metallic character will be decreased.
  • All the elements follow the common properties of metals except a few transition metals such as Zn, Cd, Mn & Hg.
  • These metals do not exhibit properties of malleability, ductility, thermal, and electrical conductivity.

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