In NOBr, the central atom is nitrogen (N). To determine the hybridization of nitrogen, we need to consider the number of electron groups around it. In NOBr, nitrogen is bonded to one oxygen atom (O) and one bromine atom (Br). Additionally, nitrogen has one lone pair of electrons.

Considering the electron groups, we can use the valence shell electron pair repulsion (VSEPR) theory to predict the molecular geometry. The presence of one lone pair and two bonded atoms creates a trigonal pyramidal electron pair geometry around nitrogen.

To accommodate this geometry, nitrogen undergoes sp3 hybridization. In sp3 hybridization, four equivalent hybrid orbitals are formed by mixing one s orbital and three p orbitals. These four sp3 hybrid orbitals have a tetrahedral arrangement, with the lone pair occupying one of the tetrahedral positions.

Therefore, the hybridization of the central atom (nitrogen) in NOBr is sp3.