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प्रश्न
Give the properties of Lanthanoids.
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
Name the radioactive element in lanthanoids.
Explain the trend in an Oxidation state of 3d elements.
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.
Which is the INCORRECT property of lanthanoids?
What is the value of effective magnetic moment found in +3 oxidation state of Chromium (Z = 24)?
The observed electronic configuration of promethium (atomic number 61) is ____________.
Which element from following forms colourless compounds in +2 oxidation state?
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.
Lanthanoids and actinoids resemble in ______.
Which of the following factors may be regarded as the main cause of lanthanoid contraction?
The most basic hydroxide from the following is:
Identify the last element in lanthanoid series.
Write expected and observed electron configurations of 58Ce.
Eu (Z = 63) and Yb (Z = 70) show + 2 oxidation state. Explain.
What are the physical properties of lanthanoids?
Write two uses of lanthanoids.
