How could mendeleev predict the properties of elements that had not yet been discovered?

Categorize them by metal, nonmetal, in periodic tableductilenon-ductilemalleableoften gain electrons easilygood conductorpoor conductorcan be liquidselements

Calculate the mass of 0.750 mol of the following substance. na3po4.

The image compares the arrangement of electrons in two different neutral atoms. a figure labeled atom q has a shaded sphere at the center of three concentric circles. the innermost circle has two black spheres. the middle circle has six black spheres. to the left of this figure is another figure labeled atom p. atom p has a shaded sphere at the center of three concentric circles. the innermost circle has two black spheres. the middle circle has seven black spheres. which of the following best explains the position of the two atoms in the periodic table?