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प्रश्न
Give the properties of Lanthanoids.
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उत्तर
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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संबंधित प्रश्न
The following electronic configuration of elements shows highest oxidation state
Name the radioactive element in lanthanoids.
Give the electronic configuration of europium (Z = 63).
Which of the following statements are FALSE about lanthanoids?
(I) They have lower heat of atomization than transition metals
(II) They are soft metals with silvery white colour and densities of about 7 g cm−3.
(III) They react with water to give the metal hydroxide and oxygen gas.
(IV) They form hydroxides, which are covalent and basic.
Which statement(s) is/are CORRECT about applications of lanthanoid metals/ions and their compounds?
(I) The optoelectronics applications use lanthanoid ions as active ions in luminescent materials.
(II) Lanthanoid compounds are used in television tubes.
(III) Lanthanoids are used in hybrid cars, superconductors and permanent magnets.
When lanthanoids (Ln) are heated to about 2800 K with carbon, the carbides with general formula ____________ are obtained.
Which element among the following lanthanoids has the smallest atomic radius?
The observed electronic configuration of promethium (atomic number 61) is ____________.
Identify the correct decreasing order of ionic radii of lanthanoids.
Which of the following properties is NOT of lanthanoids?
Identify the formula of lanthanoid oxide formed when lanthanoid (Ln) is burnt in oxygen.
Which among the following lanthanoids has smallest atomic size?
Which of the following factors may be regarded as the main cause of lanthanoid contraction?
Identify the last element in lanthanoid series.
Give the electronic configuration of gadolinium (Z = 64).
Eu (Z = 63) and Yb (Z = 70) show + 2 oxidation state. Explain.
What are the physical properties of lanthanoids?
Write two uses of lanthanoids.
Define actinoid contraction.
Which from following is a lanthanoid element?
