# Why does H₂Se have a bigger Ka2 than H₂Te

Why does $\ce{H2Se}$ have a bigger $K_\text{a2}$ than both $\ce{H2S}$ and $\ce{H2Te}$?

• What do you mean with "$Ka_2$"? – Philipp Mar 24 '15 at 19:40
• @Philipp $K_{a2}$ refers to the second dissociation constant i.e. the equilibrium constant of $\ce {HA^{-}<=> H+ + A^{2-}}$ – Binary Geek Mar 24 '15 at 19:46
• Would you mind to provide the data and the source? – Klaus-Dieter Warzecha Mar 24 '15 at 20:01

Note that $\mathrm{pK_{a1}}$ of $\ce{H2Te}$ was determined at 18 °C, all other data at 25 °C