Orbital Diagrams of Atoms

For many purposes, electron configurations are sufficient to describe the arrangements of electrons in atoms. Sometimes, however, it is useful to go a step further and show how electrons are distributed among orbitals. In such cases, orbital diagrams are used. Each orbital is represented by parentheses (), and electrons are shown by arrows written f or, depending on spin. 

To show how orbital diagrams are obtained from electron configurations, consider the boron atom (Z = 5). Its electron configuration is ls22s22p1. The pair of electrons in the Is orbital must have opposed spins (+j, or f j). The same is true of the two electrons in the 2s orbital. There are three orbitals in the 2p sublevel. The single 2p electron in boron could be in any one of these orbitals. Its spin could be either up or down. The orbital diagram is ordinarily written 

With the next element, carbon, a complication arises. In which orbital should the sixth electron go It could go in the same orbital as the other 2p electron, in which case it would have to have the opposite spin, [. It could go into one of the other two orbitals, either with a parallel spin, f, or an opposed spin, Experiment shows that there is an energy difference among these arrangements. The most stable is the one in which the two electrons are in different orbitals with parallel spins. The orbital diagram of the carbon atom is 

Similar situations arise frequently. There is a general principle that applies in all such cases Hund s rule (Friedrich Hund, 1896-1997) predicts that, ordinarily, 

Orbital diagrams for atoms with five to ten electrons. Orbitals of equal energy are all occupied by unpaired electrons before pairing begins. 

With the next element, carbon, a complication arises. In which orbital should the sixth electron go It could go in the same orbital as the other 2p electron, in which case it would have to have the opposite spin, It could go into one of the other two orbitals, 

Only after all the orbitals are half-filled do electrons pair up in orbitals. 

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Fig. 8 The molecular orbital diagrams of atomic iron before (a) and after (b) hybridization under imaginary O symmetry. (Square brackets indicate degeneracy forced by symmetry electrons were omitted for simplicity.) (c) Lowering (imaginarily) the symmetry from O to C y lifts certain degeneracy constrains, (d) spUtting into two symmetry-fOTced degenerate o-acceptor orbital clusters, under the (e) assumption o-donation fiom three /-CO will go into o-acceptor orbital cluster II...

The electron configuration or orbital diagram of an atom of an element can be deduced from its position in the periodic table. Beyond that, position in the table can be used to predict (Section 6.8) the relative sizes of atoms and ions (atomic radius, ionic radius) and the relative tendencies of atoms to give up or acquire electrons (ionization energy, electronegativity). 

Construct orbital diagrams for atoms of sulfur and iron. 

Let s look at the ground state electron configuration and orbital diagram of the beryllium atom (4Be) which is the first element in group 2A. 

Use the aufbau principle to write complete electron configurations and complete orbital diagrams for atoms of the following elements sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, and argon (atomic numbers 11 through 18). 

Electron Configurations and Partial Orbital Diagrams for Atoms of Period 4 Elements... 

In this section, you have seen how a theoretical idea, the quantum mechanical model of the atom, explains the experimentally determined structure of the periodic table, and the properties of its elements. Your understanding of the four quantum numbers enabled you to write electron configurations and draw orbital diagrams for atoms of the elements. You also learned how to read the periodic table to deduce the electron configuration of any element. 

The correct answer is (E). There are two ways to approach this. The first is to simply have memorized that when 6 electron pairs are found around a central atom, the hybridization has to be cfsp3. The other way is to consider the orbital diagram of sulfur Unhybridized S atom... 

Orbital diagram of the methyl cation. The methyl cation is similar to BH3. The carbon atom is a bonded to three hydrogen atoms by overlap of its sp2 hybrid orbitals with the s orbitals of hydrogen. A vacant p orbital lies perpendicular to the plane of the three C —H bonds. 

The section of the periodic table that contains the inner transition metals is called the/ block. Thus we can predict that the last electrons added to the orbital diagrams of elements with atomic numbers 57 through 70 would go into the 4/sublevel. Elements 89 through 102 are in the second row of the/block. Because the fourth principal energy level is the first to have an/sublevel, we can predict that the highest energy-electrons for these elements go to the 5/sublevel. 

There are three bonding pairs and no lone pair on the A1 atom. From Table 10.1 we see that the shape of three electron pairs is trigonal planar, and from Table 10.4 we conclnde that A1 mnst be ip -hybridized in AII3. The orbital diagram of the gronnd-state A1 atom is... 

Answer We note that the C atom (a second-period element) has a double bond therefore, it is p -hybridized. The orbital diagram of the O atom is... 

Figure 1.5 (a) Diagram of atomic orbitals and sp -hybridization, (b) hybrid orbitals of carbon. 

State Hund s rule in your own words, and show its application in the orbital diagram of the nitrogen atom. 

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