Potassium ground state electronic configuration

Table 8.3 shows the partial orbital diagrams and ground-state electron configurations for the 18 elements in Period 4 (again with filled inner levels in brackets and the sublevel to which the last electron has been added in colored type). The first two elements of the period, potassium and calcium, are the next alkali and alkaline earth metals, respectively, and their electrons fill the 45 sublevel. The third element, scandium (Z = 21), is the first of the transition elements, those in which d orbitals are being filled. The last electron in scandium occupies any one of the five 3d orbitals because they are equal in energy. Scandium has the electron configuration [Ar] 4s 3d. ... 

Figure 5.12 Radial wavefunctions P /r) with n = 3 for neutral chlorine (Cl I), singly-ionized argon (Aril), and doubly-ionized potassium (Kill) which demonstrate the collapse of the 3d orbital (all these systems have the electron configuration ls22s22p63s23p5 in the ground state while the results apply to the. .. 3s23p4( D)3d 2S states). Note that the horizontal scales are slightly different, but the distance from the origin to (3s + 3p)/2 is the same in all three cases. It is the average position 3s and , i.e., the 3d orbital is clearly uncollapsed. The opposite is true for Kill where the 3d orbital has clearly collapsed. The 3d orbital of Aril falls between these two cases. From [SHa83].

The alkali metals - lithium, sodium, potassium, rubidium, caesium and francium - are members of group 1 of the periodic table, and each has a ground state valence electronic configuration ns. Discussions of these metals usually neglect the heaviest member of the group, francium. Only artificial isotopes of francium are known, the longest Uved, Fr, having n = 21.8 min. 

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