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The S-Block Elements

Question
CBSEENCH11007180
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Why are potassium and caesium, rather than lithium used in photoelectric cells?

Solution
Potassium and caesium are  used in photoelectric cells rather than lithium because potassium and caesium have much lower ionisation enthalpy than that of lithium. As a result, these two metals when subjected to light, emit electrons but lithium does not. Hence potassium and caesium, rather than lithium are used in photoelectric cells.

Some More Questions From The s-Block Elements Chapter

What are s-block elements?

Why are alkali metals not found in nature?

Lithium shows similarities to magnesium in the chemical behaviour. What is the cause of this similarity?

What is the nature of lithium compounds?

Group 1 elements are called alkali metals. Why?

Why caesium can be used in photoelectric cell while lithium can not be?

In aqueous solution, Li+ ion has lowest mobility. Why?

Lithium has highest ionisation energy in group 1 elements, yet it is strongest reducing agent. Comment.

The softness of group 1 elements increases down the group with increasing atomic number. Give reason. 

Which is the most reactive alkali metal and why?

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