Write one pair of isobars

Write one pair of isobars. Why the chemical properties of isobars are not similar?

${}{18}^{40}Ar$ and
${}
{20}^{40}Ar$are isobars. Chemical properties of elements largely depend on their electronic configuration and as*the isobars of elements have different atomic number and so, also the electronic configuration, therefore, they have different chemical properties.