Which one is least ionic in nature and decompose on heating ?
Correct answer: A. LiOH
- A. LiOH
- B. NaOH
- C. KOH
- D. CsOH
Explanation
LiOH has the greatest covalent character among the alkali-metal hydroxides because the small Li+ ion strongly polarizes OH−. On heating, it decomposes: 2LiOH → Li2O + H2O, whereas the heavier alkali hydroxides are more ionic and thermally stable. Students may choose CsOH because cesium is the largest ion, but larger cations polarize hydroxide less and make the hydroxide more ionic.
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About Reactions of Group I Elements
Group I elements have one valence electron, so their reactivity increases down the group as ionisation energy decreases. Their reactions with water, oxygen, hydrogen and halogens produce hydroxides, oxides, hydrides and halides, while the behaviour of lithium differs from the heavier metals because of its small ionic size.
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