In this example problem, we write an electron configuration for lead using the periodic table. Our problem reads: write the expanded and shorthand forms of the electron configuration for lead. We'll start with a periodic table. We can divide the periodic table by quantum blocks. Our first two columns, including helium, make up our s-block. Our last six columns make up our p-block. Our transition metals make up our d-block, and our inner transition metals make up our f-block. The s subshell starts when N equals 1, the p subshell starts when N equals 2, the d subshell starts when N equals 3, and the f subshell starts when N equals 4. We can continue to fill in our end values for each of our rows and blocks in the periodic table. Now, we can write our expanded electron configuration for lead. According to the Aufbau principle, we can build up to the electron configuration for lead by adding electrons to the lowest energy available orbital. We begin by adding two electrons to the 1s orbital, which is the lowest energy orbital available. Two electrons are needed to fill an S subshell because we have two groups in that block. After helium, comes lithium, which is still in the S block. So, our next lowest energy orbital that's available is the 2s subshell. After beryllium, we go to boron, and boron begins to fill our 2p subshell. To completely fill a p subshell requires six electrons because there are six columns in the p block. After neon, we go back to sodium, which is in our s block. So, to fill from sodium to magnesium, we fill the 3s 2. Aluminum begins the 3p subshell, so aluminum to argon is 3p 6. Potassium begins the 4s subshell, so potassium to calcium is filling 4s 2. Our d-block begins when N equals 3, so we need to fill our 3d subshell. There are 10 columns in the d block, so to fill the 3d subshell, we need 10 electrons. Next, gallium begins the 4p subshell, so gallium to krypton is 4p 6. And then, 5s 2 and 4d 10 to get to cadmium. To get to xenon, we fill 5p 6. Then, to barium, it's 6s. And now, we need to go through the inner transition metals for f 14. There are 14 columns in our inner transition metals. And then, we continue filling through mercury, 5d 10. And we have two electrons in the 6p subshell to get to lead. So, this is the expanded form of our electron configuration. For the shorthand method of the electron configuration, we start with the noble gas that precedes the element in question. The noble gas that precedes lead is xenon. To figure out what s subshell we're in, we count down six rows. So, to get to barium, we're filling 6s 2. We know that the f subshell begins with four, so it's 4f 14. And then, to get to mercury, we're filling our 5d 10. And there are two electrons in our 6p subshell. So, our shorthand electron configuration is xenon 6s 2, 4f 14, 5d 10, 6p 2.