Lakhmir Singh Solutions Class 10 Chemistry Solutions for Exercise in Chapter 5 - Chapter 5 Periodic Classification of Elements

Question 65 Exercise

(a) How does the atomic size vary on going down from top to bottom in a group of the periodic table? Why does it vary this way?

(b) Lithium, sodium and potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements? Explain your answer.


(a) The main characteristic of the last elements in a period is that they all have 8 valence electrons in their atoms except helium. Such elements are generally called noble elements which have stable electronic configurations.

(b) The similarity between Lithium, Sodium, and Potassium are:

They have only one valence electron in their outermost shells, making them extremely unstable. As a result, they easily react with water to produce hydrogen. They are also called alkali metals.

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