Imagine that you are an environmental scientist. Working in collaboration with a university chemist, you were able to determine from mass spectrometry that four elements exist in your soil samples. They are Se, Sn, Pb, and Cd.

You need to determine which elements will most likely combine with oxygen to produce oxides that are present in your sample. To do so, refer to the periodic table to determine the electron configuration and ionization energy of each element. This will show the number of valence electrons for each element.

• What are the electron configurations for Se, Sn, Pb, and Cd?
• What are the valence electrons for Se, Sn, Pb, and Cd?
• Rank the elements in increasing ionization energy.
• Which element will form oxides?