[en] The interacting boson model with isospin (IBM-3) has been used to study the mixed symmetry states and electromagnetic transition properties at low spin for "2"8Si. The theoretical calculations are in agreement with experimental data. The interacting boson model (IBM) is one algebraic model describing the nucleus collective motion, which was introduced by Arima and Iachello. In the Bohr and Mottelson theory (BBM), the nucleus is anentity with geometry shape and the nucleus collective motion is studied by using dynamic variables of the transformation parameters. The IBM reveals the new dynamic symmetric characters and establishes the wave functions based on degrees of freedom of boson and group method. IBM model is a very effective phenomenological model for describing low-lying collective motions of nuclei. In the original version (IBM-1), only one kind of boson is considered, and it has been successful in describing various properties of medium and heavy even-even nuclei. The proton and the neutron in the heavy nuclei lie in different major shells and the bosons are further classified into proton-boson and neutron-boson in IBM-2. In IBM-2, mixed symmetry in the proton and neutron degrees of freedom has been predicted, and discovered in electron-scattering experiment. For lighter nuclei, the valence protons and valence neutrons are filling the same major shell and the isospin should be taken into account, so the IBM has been extended to the interacting boson model with isospin (IBM-3). In the IBM-3, three types of bosons including proton-proton boson (sπ, dπ), neutron-neutron boson (s_ν, dν) and proton-neutron boson (s_δ, d_δ ). The three s-boson and three d-boson form the isospin T = 1 triplet. (authors)