Հարց 75

A freshly cut alkali metal starts bright but soon becomes dull in ordinary air. What best explains this family-specific observation?

The metal changes into a gas at once.
Its exposed surface reacts rapidly with air.Ճիշտ պատասխան
The interior permanently loses all metallic properties.
Air polishes the surface into a dull layer.

Բացատրություն

The exposed surface rapidly reacts with substances in air, creating a tarnished layer that hides the metallic shine. Permanent brightness would imply little surface reaction and contradict the quick change that was observed.

Բացատրություն

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