The analysis of spectra is at the forefront of astrophysics research since it can provide us with a rich amount of information on the structure of the universe. The spectral modelling packages, which aid this analysis, such as Cloudy, are heavily reliant upon the atomic data available for each ion. In this work, the atomic data, both radiative and collisional, for Sc II, Mn V, S III and Mg VIII have been advanced. At each stage, the accuracy of the data have been carefully assessed via theoretical and observational comparisons. All the data have now been incorporated into Cloudy's new database - Stout, making it widely available to the astrophysics community. For Sc II, collision strengths and A-values were determined using the RMATRXII and CIV3 codes respectively, for an 89 level model. A Cloudy model was created for the Strontium filament of Eta -Carinae and the theoretical line intensities were compared with HST spectra. Two models, consisting of 125 levels, were created for Mg VIII. The models were used to determine the best set of transition probabilities and collision strengths for use in the modelling of the solar corona. The theoretical line intensities were generated and compared with the SERTS-89 and SUMER spectra. An existing S III collision strength model was extended to enable an examination of allowed emission lines from the 10 plasma torus. The theoretical spectrum was produced using Cloudy and was compared with the FUSE and EUVE spectra. Four models, consisting of 80 levels, were created for Mn V. The different models were constructed to enable a comparison ofthe Breit-Pauli, ICFT and DARC R-matrix codes. A new set of A-values was also produced using CIV3. A Cloudy model was created for NGC 7009 and t he identification of 14 [Mn V] emission lines in the spectrum was investigated.