Water has a density of 1g/cm3.If an object has a density greater than this,it will sink.Which group 1 elements will float on water and which wil sink?

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jerichorayel | College Teacher | (Level 2) Senior Educator

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Density is a property of a material that measures its mass per unit volume it occupies. Water has a density of 1 g/cm^3 and anything that has a density higher than that of water will sink. Group 1 elements are also called alkali metals. Their names, formula, and densities(in `(g)/(cm^(3))` ) are as follows:

Lithium, Li, 0.534

Sodium, Na, 0.968

Potassium, K, 0.89

Rubidium, Rb, 1.532

Caesium, Cs, 1.93

Francium, Fr, 1.87*


From the criteria of buoyancy, only elements Rubidium, Caesium and Francium will sink in water. 


*The density of francium is not yet fully understood due to some nuclear issues.

**Placing Alkali metal on water are extremely dangerous. Their reactions are explosive.