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Group 1 elements have similar physical and chemical properties because they all have one electron in the outer shell of their atoms.

• low density. The first three – lithium, sodium and potassium – are less dense than water and therefore float on water.
• very soft. They are easily cut with a knife.
• shiny when first cut, but tarnish rapidly in air.
• low melting points. The melting points decrease as the atoms get bigger going down the group.