According to NCERT , both manganate ($MnO_4^{2-}$) and permanganate ($MnO_4^-$) ions exhibit tetrahedral geometry. The bonding in these oxoanions involves both sigma and \pi character. The $\pi$-bonding is specifically formed by the lateral overlap of the filled $p$-orbitals of the oxygen atoms with the empty $d$-orbitals of the central manganese atom (known as $p\pi-d\pi$ bonding).