Explain fluorine is non-metallic while iodine has some metallic character.


Fluorine due to its high ionisation potential is non-metallic in nature whereas iodine exhibits some metallic character as it has comparatively low ionisation potential and can lose electron in certain reactions to form a cat ion, I+.

Why the elements of group VII A or group 17 are called halogens?

The elements group 17 are collectively known as halogens. The name halogen is derived from Greek words ‘halos’ and ‘gens’ meaning sea salt producer because chloride, bromine and iodine occur as salt in sea water.

Halogen molecules are coloured. Explain.

All halogen molecules are coloured. Fluorine pales in  yellow, chlorine is greenish and yellow and the  bromine is more reddish brown while iodine is shining greyish violet solid at room temperatures. Vapours of iodine are violet. The colour of halogens is due to the fact that their molecules absorb visible light radiations. This results in the excitation of valence electrons to their higher energy levels. The value of excitation energy depends upon the size of the atoms. Smaller the size, greater is the energy required for excitation. Fluorine due to its small size requires a large amount of energy for excitation and absorbs violet light of high energy. Therefore, it appears yellow. Iodine due to its large size requires smaller excitation energy and absorbs yellow light of lower energy. Hence, it appears violet. Similarly, the colour of other halogens can be accounted for on the basis of light absorbed and transmitted by them.

Explain why fluorine exhibits an oxidation state, -1 while other members of the family exhibit oxidation state -1, +1, +3, +5 and +7.

Fluorine being the most electro negative element, does not exhibit positive oxidation states. It has only one half filled 2p orbital. Therefore, it is monovalent. Since, its valence shell has no vacant d-orbital’s in which the electrons from ns and np orbital’s can be excited. So, number of unpaired electrons increase. Hence, these show higher oxidation states.

Why bond energy of fluorine is less than that of Cl2?

                lower value of bond dissociation energy is case of F2 is due to the strong repulsion between the non-bonding electrons in fluorine atoms due to the small size of F2. Another reason is the absence of the possibility of multiple bonding because of non-availability of d-orbitals.
which member of the halogen family is most expected to exhibit positive oxidation state and why?
               iodine is most expected to exhibit positive oxidation states because in moving down the group, ionisation potential goes on decreasing and hence, tendency to form positive ions increase down the group.

Visit www.topposts.in for more and latest news