![]() ![]() This is reflected in the structure of the periodic table.Īfter the 4s subshell is filled, the 3 d subshell is filled with up to 10 electrons. Figure 8.14 The 4s Subshell The 4s subshell is filled before the 3d subshell. Instead of filling the 3 d subshell next, electrons go into the 4 s subshell (Figure 8.14 “The 4s Subshell”). Figure 8.13 The 3p Subshell Next, the 3p subshell is filled with electrons. Next, the 3 p subshell is filled with the next six elements (Figure 8.13 “The 3p Subshell”). Figure 8.12 The 3s Subshell Now the 3s subshell is being occupied. The elements when this subshell is being filled, Na and Mg, are back on the left side of the periodic table (Figure 8.12 “The 3s Subshell”). The next subshell to be filled is the 3 s subshell. Figure 8.11 The 2p Subshell For B through Ne, the 2p subshell is being occupied. On the right side of the periodic table, these six elements (B through Ne) are grouped together (Figure 8.11 “The 2p Subshell”). Figure 8.10 The 2s Subshell In Li and Be, the 2s subshell is being filled.įor the next six elements, the 2 p subshell is being occupied with electrons. Figure 8.10 “The 2s Subshell” shows that these two elements are adjacent on the periodic table. The next two electrons, for Li and Be, would go into the 2 s subshell. Figure 8.10 “The 2s Subshell” shows that these two elements are adjacent on theperiodic table. Figure 8.9 The 1s Subshell The next two electrons, for Li and Be, would go into the 2s subshell. These two elements make up the first row of the periodic table (see Figure 8.9 “The 1s Subshell”). Their electron configurations are 1 s 1 and 1 s 2, respectively with He, the n = 1 shell is filled. Why does the periodic table have the structure it does? The answer is rather simple, if you understand electron configurations: the shape of the periodic table mimics the filling of the subshells with electrons. The elements are listed by atomic number (the number of protons in the nucleus), and elements with similar chemical properties are grouped together in columns. Determine the expected electron configuration of an element by its place on the periodic table.Ī periodic table is shown in Figure 8.8 “The Periodic Table”.Relate the electron configurations of the elements to the shape of the periodic table.The valence electrons are held closer towards the nucleus of the atom. This means that the nucleus attracts the electrons more strongly, pulling the atom's shell closer to the nucleus. The effect of increasing proton number is greater than that of the increasing electron number therefore, there is a greater nuclear attraction. However, at the same time, protons are being added to the nucleus, making it more positively charged. This is because, within a period or family of elements, all electrons are added to the same shell. Atomic radius patterns are observed throughout the periodic table.Ītomic size gradually decreases from left to right across a period of elements. The covalent radii of these molecules are often referred to as atomic radii. Nevertheless, it is possible for a vast majority of elements to form covalent molecules in which two like atoms are held together by a single covalent bond. Some are bound by covalent bonds in molecules, some are attracted to each other in ionic crystals, and others are held in metallic crystals. However, this idea is complicated by the fact that not all atoms are normally bound together in the same way. The atomic radius is one-half the distance between the nuclei of two atoms (just like a radius is half the diameter of a circle). ![]() ![]() This is caused by the increase in atomic radius. Electron affinity decreases from top to bottom within a group.This is caused by the decrease in atomic radius. Electron affinity increases from left to right within a period.This causes the electron to move closer to the nucleus, thus increasing the electron affinity from left to right across a period. Moving from left to right across a period, atoms become smaller as the forces of attraction become stronger. With a larger distance between the negatively-charged electron and the positively-charged nucleus, the force of attraction is relatively weaker. This means that an added electron is further away from the atom's nucleus compared with its position in the smaller atom. \( \newcommand\): Periodic Table showing Electron Affinity TrendĮlectron affinity generally decreases down a group of elements because each atom is larger than the atom above it (this is the atomic radius trend, discussed below). ![]()
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