The Mendeleev and Moseley periodic charts had

gaps for undiscovered elements. Why do you think the chart used by Moseley was more accurate at predicting where new elements would be placed?

Answer: The Moseley chart was based on using the atomic mnumber of the element, not the chemical properties. Because of the similarities between elements of the same period, this often created problems in establishing an order; Moseley's work enabled the change of the atomic number from an arbitrary selection to a definable property, measurable through experimentation.