Unit 6. Transition metals
| Unit 6 | Transition Metals |
|---|---|
| 6.1 | Explain characteristics of transition metals. |
| 6.2 | Explain oxidation states of transition metals. |
| 6.3 | Describe complex ions and metal complexes. |
| 6.4 | Show shapes of complex ions. |
| 6.5 | Describe d-orbitals in complex ions (simple explanation by crystal field theory) for octahedral complex. |
| 6.6 | Explain reasons for the colour of transition metal compounds. |
| 6.7 | Explain catalytic properties of transition metals. |
Introduction
Three series of elements formed by filling the 3d, 4d, and 5d shells of electrons are called d-block elements.
The electronic configuration of d-block elements are generally represented
by (n-1)d^1-10 ns^1-2 . Where (n-1) is penultimate shell.
In s-block and p-block element, the outermost orbital is filled. But in the d-block element electrons are added to the penultimate shell.
They are often called ‘transition elements’ because their position in the periodic table is between the s-block element( which formed ionic compound ) and the p-block element( which are largely covalent ).
Transition series
- There are three complete rows of ten elements and one incomplete row in d-block of periodic table.
- These rows are called first, second, third, and fourth transition series which involves filling of 3d, 4d, 5d, and 6d orbitals respectively.
- These series are also called transition series.
- First transition series: It contains ten elements from Scandium(At. No. 21) to Zinc (At. No. 30). They have incomplete 3d-orbitals.
- Second transition series: It contains ten elements from Yttrium (At. No. 39) to Cadmium(At. No. 48). They have incomplete 4d-orbitals.
- Third transition series: It contains ten elements with incomplete 5d�-orbitals and constitute elements Lanthanum (At. No. 57) and from Hafnium (At. No. 72) to Mercury(At. No. 80).
- Fourth transition series: It has incompletely filled f-group elements. This consist of Lanthanide and actinides.