  We study the influence of mass splitting between the charged and neutral
pions and kaons in the Juelich meson exchange model for $\pi\pi$ and $\pi\eta$
scattering. The calculations are performed in the particle basis, which permits
the use of physical masses for the pseudoscalar mesons and a study of the
distinct thresholds associated with the neutral and the charged kaons. Within
this model we also investigate the isospin violation which arises from the mass
splitting and an apparent violation of G-parity in $\pi\pi$ scattering which
stems from the coupling to the $K\overline{K}$ channel. Nonvanishing cross
sections for $\pi\pi \rightarrow \pi^{0}\eta$ indicate a mixing of the
$f_{0}(980)$ and $a_{0}(980)$ states.
