What are the characteristics of the transition elements and why are they called transition elements? Which of the d-block elements may not be regarded as the transition elements?
What are the characteristics of the transition elements and why are they called transition elements? Which of the d-block elements may not be regarded as the transition elements?
Transition elements are those elements in which the atoms or ions (in stable oxidation state) contain partially filled d-orbital. These elements lie in the d-block and show a transition of properties between s-block and p-block. Therefore, these are called transition elements. Elements such as Zn, Cd, and Hg cannot be classified as transition elements because these have completely filled d-subshell.
Characteristics of the transition elements (d-Block)
1. Electronic configuration General configuration of these elementi (n−1)d1−10ns1−2.
2. Physical properties These elements have metallic properties such as metallic lustre, high tensile strength, ductility, malleability, high thermal and electrical conductivity, low volatility (except Zn, Cd, Hg), hardness. etc. Their melting points are high.
3. Atomic and ionic size In a given series, there is a progressive, . decrease in radius with increasing atomic number.
4. Ionisation enthalpies Due to an increase:in. nuclear charge whicii accompanies the filling of inner d-orbitals, there is an increase4 . ionisation enthalpy along each series of the transition elements from left to right.
ScTiVCrMnFeCoNiCuZn+2+2+2+2+2+2+2+1+2+3+3+3+3+3+3+3+3+2+4+4+4+4+4+4+4+5+5+5+6+6+6+7
5. Oxidation states These elements exhibit variable oxidation states e,g., I Transition series:
6. Trends in M2+/ME∘ values The general trend ran less negative E∘ values across the series is related to the general increase in the sum of the first and second ionisation enthalpies.
7. Trends in M3+/M2+E∘ values Low value of E∘ shows the stability of ion (either d5 or d10 configuration).
8. Magnetic properties These elements show diamagnetism and paramagnetism.
9. Formation of coloured salts The compounds of transition elements form coloured ions, e.g., Mn3+ violet; Fe2+ green, etc.
10. Complex formation These elements form complex compounds due to their small size and high charge density. e. g., [PtCl4]2−
11. Catalyst Many of these elements are used as catalyst e.g., V2O5 is used as a catalyst in contact process for the manufacture of H2SO4
12. Interstitial compound formation Transition elements form interstitial compounds It means the compounds in which H, C or N etc. are trapped inside the crystal lattices of metals.
13. (i) Alloy formation Because of similar radii and other characteristics alloys are readily formed by these metals.
(ii) The d-block elements are called transition elements Because these elements represent change or transition in properties from s-block to p-block elements.
(iii) The electronic configuration of Zn, Cd and Hg is represented by the general formula (n−1)d10ns2. These elements have completely filled d-orbitals in ground state as well as in their common oxidation states. Therefore, they may not be regarded as the transition elements.
Transition elements are those elements in which the atoms or ions (in stable oxidation state) contain partially filled d-orbital. These elements lie in the d-block and show a transition of properties between s-block and p-block. Therefore, these are called transition elements. Elements such as Zn, Cd, and Hg cannot be classified as transition elements because these have completely filled d-subshell.
Characteristics of the transition elements (d-Block)
1. Electronic configuration General configuration of these elementi (n−1)d1−10ns1−2.
2. Physical properties These elements have metallic properties such as metallic lustre, high tensile strength, ductility, malleability, high thermal and electrical conductivity, low volatility (except Zn, Cd, Hg), hardness. etc. Their melting points are high.
3. Atomic and ionic size In a given series, there is a progressive, . decrease in radius with increasing atomic number.
4. Ionisation enthalpies Due to an increase:in. nuclear charge whicii accompanies the filling of inner d-orbitals, there is an increase4 . ionisation enthalpy along each series of the transition elements from left to right.
ScTiVCrMnFeCoNiCuZn+2+2+2+2+2+2+2+1+2+3+3+3+3+3+3+3+3+2+4+4+4+4+4+4+4+5+5+5+6+6+6+7
5. Oxidation states These elements exhibit variable oxidation states e,g., I Transition series:
6. Trends in M2+/ME∘ values The general trend ran less negative E∘ values across the series is related to the general increase in the sum of the first and second ionisation enthalpies.
7. Trends in M3+/M2+E∘ values Low value of E∘ shows the stability of ion (either d5 or d10 configuration).
8. Magnetic properties These elements show diamagnetism and paramagnetism.
9. Formation of coloured salts The compounds of transition elements form coloured ions, e.g., Mn3+ violet; Fe2+ green, etc.
10. Complex formation These elements form complex compounds due to their small size and high charge density. e. g., [PtCl4]2−
11. Catalyst Many of these elements are used as catalyst e.g., V2O5 is used as a catalyst in contact process for the manufacture of H2SO4
12. Interstitial compound formation Transition elements form interstitial compounds It means the compounds in which H, C or N etc. are trapped inside the crystal lattices of metals.
13. (i) Alloy formation Because of similar radii and other characteristics alloys are readily formed by these metals.
(ii) The d-block elements are called transition elements Because these elements represent change or transition in properties from s-block to p-block elements.
(iii) The electronic configuration of Zn, Cd and Hg is represented by the general formula (n−1)d10ns2. These elements have completely filled d-orbitals in ground state as well as in their common oxidation states. Therefore, they may not be regarded as the transition elements.
