Answer (score: 1): 15. Select three elements that are in the same period in the Periodic Table of Chemical Elements by D.I. Mendeleev , and arrange the selected elements in order of increasing ionization energy. 1) P 2) Sb 3) Rb 4) Sn 5) Zn

The correct answer is: 3) Rb, 1) P, 5) Zn.<br /><br />Explanation: In the Periodic Table, elements in the same period have the same number of electron shells. The ionization energy of an element is the energy required to remove an electron from a neutral atom. Ionization energy generally increases across a period from left to right. Therefore, the order of increasing ionization energy for the given elements is Rb (Rubidium), P (Phosphorus), and Zn (Zinc).