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Post a LessonAnswered on 10 Apr Learn Unit 10-s -Block Elements (Alkali and Alkaline Earth Metals)
Sadika
Physical and Chemical Features of Alkali Metals:
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Answered on 10 Apr Learn Unit 10-s -Block Elements (Alkali and Alkaline Earth Metals)
Sadika
Characteristics of Alkaline Earth Metals:
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Answered on 10 Apr Learn Unit 10-s -Block Elements (Alkali and Alkaline Earth Metals)
Sadika
Absence of Alkali Metals in Nature: Alkali metals are highly reactive and readily react with moisture and oxygen in the atmosphere, making them unstable in their pure form. They are typically found in nature as compounds rather than as pure metals.
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Answered on 10 Apr Learn Unit 10-s -Block Elements (Alkali and Alkaline Earth Metals)
Sadika
Oxidation State of Sodium in Na2O2: In Na2O2Na2O2, each oxygen atom is in the peroxide ion (O22−O22−). Since the overall charge of the compound is 0, sodium must be in the +1 oxidation state to balance the negative charges from the peroxide ions. So, the oxidation state of sodium in Na2O2Na2O2 is +1.
read lessAnswered on 10 Apr Learn Unit 10-s -Block Elements (Alkali and Alkaline Earth Metals)
Sadika
Reactivity of Sodium vs. Potassium: Sodium is less reactive than potassium because sodium has a larger atomic radius and higher ionization energy compared to potassium. These factors make it more difficult for sodium to lose an electron and react with other substances compared to potassium.
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Answered on 10 Apr Learn Unit 10-s -Block Elements (Alkali and Alkaline Earth Metals)
Sadika
Comparison of Alkali Metals and Alkaline Earth Metals:
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Answered on 10 Apr Learn Unit 10-s -Block Elements (Alkali and Alkaline Earth Metals)
Sadika
Similarities between Lithium and Magnesium: Both lithium and magnesium are relatively hard metals with low densities. They have high melting and boiling points compared to other alkali metals and alkaline earth metals, respectively. They also form covalent compounds (e.g., organolithium and organomagnesium compounds) in addition to ionic compounds.
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Answered on 10 Apr Learn Unit 10-s -Block Elements (Alkali and Alkaline Earth Metals)
Sadika
Obtaining Alkali and Alkaline Earth Metals by Chemical Reduction: Alkali and alkaline earth metals cannot be obtained by chemical reduction methods because they are highly reactive and readily form positive ions. Even in their ore forms, they exist as ionic compounds and cannot be reduced directly by chemical means. Instead, these metals are typically obtained through electrolytic processes or by reaction with other metals in certain conditions.
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Answered on 13 Apr Learn Unit 10-s -Block Elements (Alkali and Alkaline Earth Metals)
Nazia Khanum
Potassium and cesium are sometimes preferred over lithium in photoelectric cells due to their lower ionization energy. Ionization energy is the energy required to remove an electron from an atom or ion in its gaseous state. Both potassium and cesium have lower ionization energies compared to lithium, making it easier to liberate electrons from their surfaces when exposed to light.
In photoelectric cells, the goal is to efficiently convert light energy into electrical energy by causing the emission of electrons from a material's surface (the photoelectric effect). Materials with lower ionization energies can release electrons more readily when illuminated by photons, leading to a more efficient conversion process.
However, the choice of material also depends on various factors such as cost, stability, and practical considerations in the specific application. While potassium and cesium may have advantages in certain cases, lithium could still be chosen for other applications where its properties are more suitable.
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Answered on 13 Apr Learn Unit 10-s -Block Elements (Alkali and Alkaline Earth Metals)
Nazia Khanum
When alkali metals like lithium, sodium, or potassium dissolve in liquid ammonia, they form solutions that exhibit interesting color changes. This phenomenon is due to the formation of solvated electrons, which are free-moving electrons surrounded by a shell of solvent molecules (in this case, ammonia molecules).
Initially, as the alkali metal dissolves, the solution appears blue due to the presence of solvated electrons. These solvated electrons are responsible for the blue coloration. However, as more metal dissolves and the concentration of solvated electrons increases, the color of the solution changes to bronze, gold, or even reddish-brown.
This change in color occurs because as the concentration of solvated electrons increases, they begin to interact with each other, forming dimers and other aggregates. These aggregates absorb light differently, leading to a change in the observed color of the solution. The exact color observed depends on factors such as the concentration of solvated electrons and the specific alkali metal involved.
Overall, the color changes observed in alkali metal solutions in liquid ammonia are due to the formation of solvated electrons and their subsequent interactions, which alter the absorption properties of the solution.
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