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Question
Give the properties of Lanthanoids.
Solution
The properties of lanthanoids are:
- Soft metals with silvery white colour and moderate densities of 7 g cm–3. Colour and brightness reduces on exposure to air.
- Good conductors of heat and electricity.
- Except for promethium (Pm), all are non-radioactive in nature.
- The atomic and ionic radii decrease from lanthanum (La) to lutetium (Lu). This is known as lanthanoid contraction.
- Binding to water is common (i.e.,) such that H2O is often found in products when isolated from aqueous solutions.
- Coordination numbers usually are greater than 6, typically 8, 9.... (up to 12 found).
- The Lonthonoides are strongly paramagnetic. Gadolinium becomes ferromagnetic below 16°C (Curie point). The other heavier Lothonoids terbium, dysprosium, holmium, erbium, thulium, and ytterbium become ferromagnetic at much lower temperatures.
- Magnetic and optical properties are Largely independent of environment (similar spectra in gas/solution/solid).
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