what is the daughter nucleus produced when 90sr undergoes beta decay

beta decay are of two types the beta plus decay and the beta minus decay, the beta plus decay releases a positron,  a proton is converted to neutron, the atomic number drop by one . therefore if strontium undergo a beta plus decay , the decay nucleus is rubidium-90.

on the other hand if strontium under a beta minus decay, a neutron is converted into proton, the atomic number increase by one while the atomic  mass remain unchanged. the daughter nucleus formed is  yttrium-211.