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The lightest known metal in the world is lithium. It is an alkali metal with a low atomic mass and density, making it extremely light compared to other metals.
Lithium is the lightest element metal with a relative atomic mass of 7 (3 protons, 4 neutrons).
The lightest 'non-metal' could be Hydrogen and Helium! Both are gases, and therefore, not a metal.
The lightest metal is lithium.
Iridium is the most strongest, rarest, densest, expensive, lightest metal ever known
Lithium is the lightest transition metal.
Boron (symbol B) with a relative mas of 10.811.
lithium
The lightest alkaline earth metal is Beryllium(Be) having atomic mass 9.012 dalton. The heaviest element in this family is radium.
Cobalt.
Helium
Alluminum is probably the lightest of coinage metals used to-date.