Chapter 5: Periodic Classifications of Elements

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Periodic Classifications of Elements


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

(b) Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?


(a)- Lithium, sodium, and potassium belong to Group 1. These elements have 1 valence electron and are univalent cation. The formation of an oxide of these elements are shown below:

Li (s) + O2 (g) → Li2O (s)

Na (s) + O2 (g) → Na2O (s)

K (s) + O2 (g) → K2O (s)

(b)- Helium and neon are inert gases and they belong to Group 18. The elements of Group 18 have filled valence electrons.

Helium (2) = 2

Neon (10) = 2, 8

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