1 pound....why do u want to know this?
The lightest alkaline earth metal is Beryllium(Be) having atomic mass 9.012 dalton. The heaviest element in this family is radium.
I have absolutely no idea!
scoria
No, water is not the lightest liquid on Earth. Liquid hydrogen and liquid helium are lighter than water because they have lower densities.
Mercury is the lightest planet, with a mass of 0.055 that of Earth.
the mantel
2111
Lithium is the lightest metal, Potassium is the second lightest -- density about 0.86 kg/L
water is the and most found substance also earth and air
Hydrogen
The least dense element is hydrogen hence it would be the lightest thing with mass. However there are 'massless' particles, such as photons.
The lightest rock on Earth is pumice, which typically has a weight of around 0.25 to 0.6 grams per cubic centimeter.