Shell model calculations of natural parity states in the 10N AN 14 mass region have been performed by assuming an inert 4He core with the residual interaction in the lp shell only. The modified surface delta interaction (MSDI) has been used as an effective two-body interaction. The MSDI parameters as well as the single-particle binding energies have been deduced from a least-squares fit to experimentally known levels in, firstly, the seperate l~ 11B--C, 12C, laC--N and 14N nuclei, and secondly, the whole mass region 10-