Table comparing model results and predicted values are shown below (Table ). The main difficulty in this kind of prediction was to capture the trend in a particular property correctly. As we know, extrapolation is not a trivial task for ML. Therefore getting the prediction of the first element (hydrogen) to get its size correctly in a given size scale was a challenging task. Once we acquired the correct trend (Figure ), which agreed with our expectations (hydrogen being the smallest element), and the statistics (RMSE) were reasonable, a similar approach was used for the rest of the properties with missing values. In total, we predicted 26 radii values in 5 size scales and 17 electronegativity values in 3 EN scales. We updated the elemental property table with the predicted values and highlighted them in yellow, so that researchers could decide whether to include this data as the basis for features.