http://www.ck12.org Chapter 6. The Periodic Table
- The element is in Period 6. In determining the group, thefelectrons can be ignored since they do not affect
groups. By adding 6 + 2 = 8, we can place the element in Group 8. The partially filleddsublevel makes it a
member of thed-block. It has 2 valence electrons. The element is osmium, a metal (specifically, a transition
metal).
Step 3: Think about your result.
Once you have identified each element, you can use the electron configurations from a periodic table to make sure
they have been identified correctly.
Practice Problems- For each of the following, identify the period, group, and block. Determine the number of valence electrons.
Identify the element by name and type (metal, nonmetal, or metalloid).
a. [Kr]4d^105 s^2
b. [Ne]3s^23 p^2 - For the two elements in problem 1 above, how many unpaired electrons are in the atom?
- Which two elements have three unpaired electrons in the 3dsublevel?
You can watch video lectures on this topic from Kahn Academy. These videos combine orbital configurations (from
the chapterElectrons in Atoms) with locations on the periodic table:
- Introduction to Orbitals at http://www.youtube.com/watch?v=yBrp8uvNAhI (13:38)
- More on Orbitals and Electron Configuration at http://www.youtube.com/watch?v=FmQoSenbtnU (14:31)
- Electron Configurations at http://www.youtube.com/watch?v=RJlEH5Jz80w (10:04)
- Electron Configurations 2 at http://www.youtube.com/watch?v=YURReI6OJsg (10:18)
Lesson Summary
- An element’s placement in the periodic table is determined by its electron configuration.
- The chemical properties of various elements are intimately related to their valence electron configurations.
- The periodic table is divided into four blocks (s,p,d,f) based on which sublevel is in the process of being
filled. - Alkali metals, alkaline earth metals, halogens, and noble gases are the common names of groups 1, 2, 17, and
18. - Transition elements are members of thed-block, while thef-block consists of the lanthanides and the actinides.
Lesson Review Problems
Reviewing Concepts
- How many elements are in the second period? The fourth? The sixth?
- Use a periodic table to identify the block in which each of the following elements would be found.
a. rubidium