Write characterstics of D block elements..
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Answers
Answer:
D block elements are the elements which can be found from the third group to the twelfth group of the modern periodic table. The valence electrons of these elements fall under the d orbital. D block elements are also referred to as transition elements or transition metals
Explanation:
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Explanation:
1 Atomic and Ionic Radii
The atomic and ionic radii of transition elements are smaller than those of p- block elements and larger than those of s-block elements. The atomic and ionic radii of first transition elements are given in the List.
Element and Atomic (pm) radii
Sc - 144
Ti - 132
V - 122
Cr - 118
Mn - 117
Fe - 117
Co - 116
Ni - 115
Cu - 117
Zn - 125
The atomic radii of first transition series decreases from Sc to Cr and remains almost constant till Cu and then increases towards the end. This can be explained based on two effects namely screening and the nuclear charge effect. These two effects oppose each other resulting in increase in nuclear charge. Hence very slight variation in the atomic radii from Cr to Cu is observed.
It has been observed that Zirconium and Hafnium have almost equal atomic radii. This is because of lanthanide contraction.
2 Metallic character
All the transition elements are metals, since the number of electrons in the outermost shell is very small, being equal to 2. They are hard, malleable and 3. Formation of coloured ions
Most of the transition metal compounds are coloured in their solid or solution form. The colour of transition metal ions is due to the presence of unpaired electrons in it and the energy gap between two energy levels in the same d-subshell beingsmall. Hence very small amount of energy is required for excitation of electrons from one energy level to the other. The energy can be easily provided by the visible light. The colour observed corresponds to the complementary colour of the light absorbed.
It may be noted that Zinc, Cadmium and Mercury salts do not form any coloured compounds because of the absence of vacant d orbitals to which electrons can be excited. Sc3+ ions are also colourless because of the absence of d-electrons.