Predict the density of Cs from the density of the following elements.
`K=0.86g//cm^(3)" Ca"=1.548g//cm^(3)" Sc"=2.991g//cm^(3)`
`Rb=1.532g//cm^(3)" Sr"=2.63g//cm^(3)" Y"=4.34g//cm^(3)`
`Cs=? " Ba"=3.51g//cm^(3)" La"=6.16g//cm^(3)`

Explanation

The elements listed above belong to group 1, 2 and 3 respectively. Let us calculate the ratios of densities of Ba and Sr present in group 2 and of La and Y which belong to group 3.
Ratio of densities of Ba and Sr `=(3.51)/(2.63) =1.33` Ratio of densities of La and 6.16 Y `=(6.16)/(4.34)=1.42`
From the values, we find the ratio increases by (1.42 – 1.31) = 0.11. Moving on the same lines, the expected ratio of the densities of Cs and Rb =1.31- 0.11 =1.20.
Thus, `("Density of Cs")/("Density of Rb")=1.20`
or Density of `Cs= 1.20 xx Density of Rb= 1.20 xx 1.532" (given) = "1.84 g/cm^(3).` The actual density of Cs is `1.87 g//cm^3` and this is quite close to the predicted vaule.