The photoelectric effect is utilized in certain light-sensitive cells. Which pair of s-block metals — s Block Elements Chemistry Question

💡 Solution & Explanation

Caesium ($Cs$) and Potassium ($K$) have very large atomic sizes and the lowest ionization enthalpies in the periodic table. Their outermost electrons are so loosely bound that even the low energy of visible light photons is sufficient to eject them, making them ideal for photoelectric cells.