four actinides—thorium, protactinium, uranium, and neptunium—have been found on Earth. The others were made in the laboratory.READING CHECK 6.Which blocks of the periodic table contain elements that are considered metals?
3. Two electrons fi ll the s sublevel fi rst, so one electron must be in the p sublevel. The outer con fi guration for a Group 13 element in the third period, n = 3, is 3 s 2 3 p 1 . The third period element in Group 13 is aluminum, Al. Aluminum is a metal. 4 CHECK YOUR WORK Determine if the answers make sense. The con fi guration of aluminum matches the group and period describing its location in the periodic table. PRACTICE Answer without looking at the periodic table. E. Write the outer electron con fi guration for the Group 14 element in the fifth period. F. Identify the following for the element with the electron con fi guration [Ar]3 d 10 4 s 2 4 p 3 . Period number Block designation Group number 146 CHAPTER 5 4 P 3 5s^2 4d^10 5p^2
SAMPLE PROBLEM Use the given electron con fi guration to determine the period, group, and block for these four elements. Then use the periodic table to name each element, identify it as a metal, nonmetal, or metalloid, and describe its relative reactivity. SOLVE Electron configuration Complete before looking at the periodic table Complete while looking at the periodic table Period Block Group Name Type Reactivity a. [Xe]4 f 14 5 d 9 6 s 1 6 d 10 platinum metal low b. [Ne]3 s 2 3 p 5 3 p 17 chlorine nonmetal high c. [Ne]3 s 2 3 p 6 3 p 18 argon nonmetal low d. [Xe]4 f 6 6 s 2 6 f N/A samarium metal high a. The 5 d sublevel is not fi lled, so the element is in the d block. The group number is 9 + 1 = 10. The element is platinum, which is a transition metal and has low reactivity. b. The 3 p sublevel is not fi lled, so the element is in the p block. The group number is 10 + 5 + 2 = 17. The element is chlorine, a reactive nonmetal.