Physical properties of alkaline earth metals.
Answer Text: Physical properties of alkaline earth metals.1. Appearance.- Alkaline earth metals acquire a metallic luster when polished. This refers to a shiny appearance on the cut surface.- They however lose this metallic luster when exposed to air due to oxidation.Note:- The purpose of polishing alkaline earth metals before using them in experiment is to remove the oxide coating that slows down and prevents them from reacting.2. Ease of cutting.- Magnesium is hard to cut with a knife; but is however malleable and ductile.- Calcium cannot also be cut with a knife because it is brittle.Note:Malleability: - Refers to the ability of a material to be hammered into sheets.Example: Iron sheets are possible to be made because iron metal is malleable.Ductility:- The ability of a material to be rolled into wires.Example: electric cables are made of aluminium because aluminium metal is ductile.Brittle:- Refers to a substance which is hard and likely to break.3. They have relatively high melting and boiling points in comparison to alkali metals.Reason: they have relatively stronger metallic bonds (than alkali metals).- The melting and boiling points decrease down the group.Reason: -- The size of the atoms increase down the group due to increasing number of energy levels. As the atomic radius increase the force of attraction between the positive nucleus and the delocalized electrons decrease. This leads to a decrease in the strength ofthe metallic bonds (down the group).4. Electrical conductivity.- Alkaline earth metals are good conductors of heat and electricity.Reason: they have delocalized electrons in the outermost energy level.- The electrical conductivity is similar for all the alkaline earth metals.Reason: all alkaline earth metals have the same number of delocalized electron (two valence electrons) in the outermost energy level.
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