Which of the following is more soluble in the ether?

• Solubility decreases with an increase in the ionic size of alkaline earth metal halides.

The cation size order is

${\mathrm{Ba}}^{2+}>{\mathrm{Sr}}^{2+}>{\mathrm{Ca}}^{2+}>{\mathrm{Be}}^{2+}$

So solubility order will be

${\mathrm{BeCl}}_2>{\mathrm{CaCl}}_2>{\mathrm{SrCl}}_2>{\mathrm{BaCl}}_2$

Also, ${\mathrm{BeCl}}_2$ is covalent and nonpolar in nature. Since, like dissolve like’ ${\mathrm{BeCl}}_2$ is more soluble in ether.