Earlier scientists made the periodic table based on the element’s chemical properties. They observed the increasing order of masses to be the common trend, except at few places.
For example: The placement of Nickel and Cobalt in periodic table. The atomic weight of Cobalt was more than Nickel and according to the atomic mass trend should have been placed after Nickel but were placed correctly due to Moseley’s objective measurements of their atomic numbers. Co 27 and Ni 28.
Moseley plotted the square root of frequency of Kα Characteristic x-ray of different elements against their position number in the periodic table.
He found out the curve to be linear.
Moseley found that the frequency of Kα Characteristic x-ray of Nickel was more than that of the Cobalt and thus put Nickel after Cobalt in the periodic table.
Moseley was convinced after his characteristic x-ray experiment that, there is another fundamental quantity which increases as regular steps as one moves from one element to the other and that was number of protons (positively charged particles inside the nucleus). Which we know today as Atomic number.
Following our discussion, not only both the statements are correct but Statement II infers to Statement I as well.