Although colored lights produce their colors, objects are colored because they preferentially reflect a certain color from the white light that shines on them. The color of objects comes from a different mechanism than the colors of neon and other discharge lights. Indeed, the electron configuration of Se is 4 s 23 d 104 p 4, as expected. This means that its electron configuration should end in a p 4 electron configuration. It is in the fourth column of the p block. Consider Se, as shown in Figure 8.20 “Selenium on the Periodic Table”. Similarity of valence shell electron configuration implies that we can determine the electron configuration of an atom solely by its position on the periodic table. However, many similarities do exist in these blocks, so a similarity in chemical properties is expected. In the d and f blocks, because there are exceptions to the order of filling of subshells with electrons, similar valence shells are not absolute in these blocks. This is strictly true for all elements in the s and p blocks. Elements in each column have the same valence shell electron configurations, and the elements have some similar chemical properties. The same concept applies to the other columns of the periodic table. The organization of electrons in atoms explains not only the shape of the periodic table but also the fact that elements in the same column of the periodic table have similar chemistry. Because much of the chemistry of an element is influenced by valence electrons, we would expect that these elements would have similar chemistry- and they do. They all have a similar electron configuration in their valence shells: a single s electron.