Boron you see with the concept of VBT has a valency of one .therefore it can form one atomic orbital .since an unpaired electrons causes a atomic orbital to come into existence therefore it has one atomic orbital
However in accordance to hybridization theory . boron has a valency of three ( after the mixture of s and p orbitals ) . therefore it can form three hybrid obitals . It depends upon which concept you are asking this from
one atomic orbital.
two atomic orbitals.
three hybrid o...