Inductively-coupled plasmas in molecular, electronegative gases are widely used for plasma processing of surfaces, for instance in CMOS manufacture. The complexity of these systems is such that they can only be described by multi-physics models which describe both the plasma physics and the molecular collisional processes. However, there has been little rigorous validation of these models by comparison to quantitative measurements of particle densities over a wide range of parameter space. We have chosen to study the Cl2/O2 system partly because of the industrial process relevance but also because methods exist to measure the density, and energy distributions, of most of the particles present. Electron densities were measured by microwave hairpin resonator. Absolute Cl and O atom densities were determined by Two-photon Absorption Laser-Induced Fluorescence [1, 2]. We have constructed a new ultra-low noise broadband UV-visible absorption bench[3], which allows the measurement of the densities of ground state Cl2 molecules and ClxOy reaction products, as well as vibrationally excited states of O2 [3] and Cl2 [4]. Gas temperatures are determined by Doppler-resolved IR laser absorption spectroscopy of argon metastable atoms (added in small quantity), and showing that high gas temperatures (up to 2000K) can be reached. This comprehensive data set will be presented, along with comparison to different (0D and 2D cylindrical) models References [1] J.P. Booth, Y. Azamoum, N. Sirse, and P. Chabert, Journal of Physics D-Applied Physics, 45, 195201. (2012) 195201 [2] N. Sirse, J.P. Booth, P. Chabert, A. Surzhykov, and P. Indelicato, Journal of Physics D: Applied Physics, 46, (2013) 295203 [3] M. Foucher, D. Marinov, E. Carbone, P. Chabert, and J.-P. Booth, Plasma Sources Science & Technology, 24, (2015) 042001 [4] D. Marinov, M. Foucher, E. Campbell, M. Brouard, P. Chabert, and J.-P. Booth, Plasma Sources Science & Technology, in press, (2016)