Why lithium is harder than others alkali metals?

1.	Why lithium is harder than others alkali metals?
Answer» Density increases as we go down the group and hardness decreases. Lithium is the lightest alkali metal and is harder than other alkali metals. As the number of shells increase, the attraction between the nucleus and the valence electrons decreases leading to a soft-weak structure that can be even cut by a knife.

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