Chapter 22: Problem 3

Write short note on (a) lanthanide contraction (b) stability of isotopes of plutonium

Short Answer

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Lanthanide contraction is due to the poor shielding of nuclear charge by 4f electrons, causing a decrease in atomic radii of lanthanides from Cerium to Lutetium. Plutonium isotopes, such as Pu-238, -239, -240, -241, and -242 are unstable because of their large nuclear size, emitting radiation over time to achieve stability.

Step by step solution

Writing a short note on lanthanide contraction

(a) Lanthanide contraction refers to the phenomenon where the atomic radii of lanthanides, elements 57-71 on the periodic table, decrease with increasing atomic number. This phenomenon is due to the poor shielding of nuclear charge by 4f electrons, leading to an increase in effective nuclear charge with an increase in atomic number. Therefore, the size of lanthanide elements decreases from cerium (Ce) to lutetium (Lu). It has significant influence on the properties of elements and their compounds.

Writing a short note on the stability of plutonium isotopes

(b) Plutonium is a radioactive chemical element with multiple isotopes, most common of which are Pu-238, Pu-239, Pu-240, Pu-241, and Pu-242. Plutonium isotopes are unstable because their large atomic nuclei have too many protons, which causes a strong repulsive force. Over time, to achieve stability, plutonium isotopes undergo radioactive decay, a process in which they spontaneously emit radiation in the form of alpha, beta, or gamma rays. Pu-239, in particular, is of interest as it can sustain a nuclear chain reaction and is used in nuclear weapons and reactors.

Short summary

To sum up: (a) Lanthanide Contraction is the phenomenon of contraction in size of the atoms in the series of lanthanides elements due to the inadequate shielding of one electron by another in 4f orbital. (b) Plutonium isotopes are unstable due to their large atomic number leading to excessive repulsive forces. To stabilize, these isotopes undergo radioactive decay.

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Write short note on (a) lanthanide contraction (b) stability of isotopes of plutonium

Short Answer

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Writing a short note on lanthanide contraction

Writing a short note on the stability of plutonium isotopes

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