Periodic table isoelectronic series

Another situation where the aforementioned condition is met is along a series of H2 A isoelectronic molecules where A varies along a row of the Periodic Table. Here, Hpq remains roughly constant and, thus, the bending force increases as AEpq decreases, a trend which obtains as the lone pair ionization potential of the central atom decreases. Typical data are shown in Scheme 8. 

For As, Sb, and Bi, there is an important series of compounds formed with the Group 13 elements. These are commonly called III-V compounds (based on the traditional group numbering in the Periodic Table) and they have important applications as semiconductors. To illustrate, GaAs is isoelectronic to silicon, but a greater range of properties can be achieved because composition can be more easily varied. The disadvantage of III-V compounds relative to silicon based semiconductors is that they are reactive towards moisture and must be encapsulated. 

Sizes of ions related to positions of elements in the periodic table. Note that size generally increases down a group. Also note that in a series of isoelectronic ions, size decreases with increasing atomic number. The ionic radii are given in units of picometers. 

We have already considered two first-row metal series containing 12 and 14 valence electrons where there are hints of adherence to the principle. However, there is a more definite exaunple of "isoelectronic" behavior where the ground states of four 13-electron molecules have been established to be E. These molecules are also in the class of what have been referred to, after Gingerich, et al. (34-36), as Brewer-Engel molecules (37) each involves two elements from opposite ends of the periodic table, in this case Groups IIIB and VIII. Such molecules are expected to form strong multiple bonds and therefore to be of low spin. ScNi, 89y105p ... 

Table 28 summarizes frequencies of Pi and P2 observed for several isoelectronic series in which it was noticed that Ap = Pi — P2 becomes smaller with increase in mass of the central atom. Similarly, Ap decreases in each group of the periodic table with increase in mass of e central atom. Including the observed values for BrF and IF5 in which Ap obtains even negative values indeed fits into the general pattern of this table. This trend is presumed to arise from a decrease in the non-bonded fluorine interactions with an increase in the size of the central atam ). 

Abstract It is the hypothesis of this chapter that diatomic molecular Franck-Condon factors echo the periodicities of atonos. This means that in isoelectronic series, entire Deslandres tables for molecules that are one proton shift away from rare-gas molecules have distinctive behavior relative to other Deslandres tables in the series. An example is in the 21-electron sequence where BeCl, whose chlorine atom is next to the closed-shell magic-number atom argon. The periodicity is found quantitatively and indeed allows for prediction of the vibration frequency for a hypothetical 11 upper state for CCl. 

Notice the positions and atomic numbers of these elements in the periodic table. The nonmetal anions precede the noble gas Ne in the table. The metal cations follow Ne. Oxygen, the largest ion in this isoelectronic series, has the lowest atomic number, 8. Aluminum, the smallest of these ions, has the highest atomic number, 13. 

Cations are smaller than their parent atoms anions are larger than their parent atoms. For ions of the same charge, size increases going down a column of the periodic table. An Isoelectronic series is a series of ions that has the same number of electrons. For such a series, size decreases with increasing nuclear charge as the electrons are attracted more strongly to the nucleus. 

Figure 29.12 Water has higher (a) melting and (b) boiling temperatures and (c) higher enthalpy of vaporization than comparable molecules. Each connected line represents a series of isoelectronic molecules, stepping downward in the periodic table. Alternate lines are broken to make them easier to follow. Source L Pauling, General Chemistry, Dover Publications, New York, 1970.

Which periodic table s highlighted portion includes elements that can form an isoelectronic series (Select all that apply.)... 

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