Chapter 7 - Periodic Properties of the Elements - Exercises - Page 291: 7.9b

The numbers in part (a) is in fact the total number of valence electrons that could add to an atom after it reaches a new row in the periodic table, corresponding to what kind of subshells it has. - If the atom has only subshell s, then the maximum number of valence electrons that could be added is 2. - If the outer shell of the atom has subshells s and p, then the maximum number of valence electrons that could be added is 8. - If the outer shell of the atom has subshells s and p and d, then the maximum number of valence electrons that could be added is 18. - If the outer shell of the atom has subshells s and p and d and f, then the maximum number of valence electrons that could be added is 32.

The atomic number of some noble gas in the periodic table are as follows: - Row 1: He (2) - Row 2: Ne (10) - Row 3: Ar (18) - Row 4: Kr (36) - Row 5: Xe (54) - Rows 6: Ra (86) We can see that the difference in atomic number between row 1 and 2 is 8, between row 2 and 3 is also 8, 3 and 4 is 18, 4 and 5 is 18, 5 and 6 is 32. The difference in atomic number found above corresponds to the numbers found in part a). Therefore, the numbers in part a) is in fact the total number of valence electrons that could add to an atom after it reaches a new row in the periodic table, corresponding to what kind of subshells it has. - If the atom has only subshell s, then the maximum number of valence electrons that could be added is 2. - If the outer shell of the atom has subshells s and p, then the maximum number of valence electrons that could be added is 8. - If the outer shell of the atom has subshells s and p and d, then the maximum number of valence electrons that could be added is 18. - If the outer shell of the atom has subshells s and p and d and f, then the maximum number of valence electrons that could be added is 32.