Please see attachment. 1. "Now the 2s orbital and two of the 2p orbitals of B hybridize to form a set of three equivalent sp2 hybrid orbitals." The notes says. Can someone tell me why are there two 2p orbitals in B? I thought electronic configuration of B is 1s2 2s2 2p1? 2. What does the [He] beside B mean? Thanks in advance.