Question:
Which of the following have minimum and maximum threshold energy K, Na, Mg, Li?
Which of the following have minimum and maximum threshold energy K, Na, Mg, Li?
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The threshold energy is directly related to ionization energy: higher ionization energy means higher threshold energy.
Updated On: Apr 18, 2026
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Solution and Explanation
Step 1: Understanding threshold energy.
Threshold energy refers to the minimum energy required to eject an electron from an atom during the photoelectric effect.
Step 2: Analyze the elements.
Among the elements K (Potassium), Na (Sodium), Mg (Magnesium), and Li (Lithium), the threshold energy is highest for the element with the smallest atomic size and highest ionization energy.
Step 3: Ionization energy trend.
Ionization energy generally increases across a period (left to right) and decreases down a group (top to bottom) in the periodic table.
Step 4: Determine the trend.
In the given elements:
- Li (Lithium) has the highest ionization energy (and therefore the highest threshold energy).
- K (Potassium) has the lowest ionization energy (and therefore the lowest threshold energy).
Step 5: Conclusion.
Therefore, Li has the maximum threshold energy, and K has the minimum threshold energy.
Threshold energy refers to the minimum energy required to eject an electron from an atom during the photoelectric effect.
Step 2: Analyze the elements.
Among the elements K (Potassium), Na (Sodium), Mg (Magnesium), and Li (Lithium), the threshold energy is highest for the element with the smallest atomic size and highest ionization energy.
Step 3: Ionization energy trend.
Ionization energy generally increases across a period (left to right) and decreases down a group (top to bottom) in the periodic table.
Step 4: Determine the trend.
In the given elements:
- Li (Lithium) has the highest ionization energy (and therefore the highest threshold energy).
- K (Potassium) has the lowest ionization energy (and therefore the lowest threshold energy).
Step 5: Conclusion.
Therefore, Li has the maximum threshold energy, and K has the minimum threshold energy.
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