Isoelectronic Having the same number

Both are ionic substances with lattice sites occupied by cations and anions. In perchloric acid monohydrate, the cation is H30+ and there are no water molecules of hydration. The cations in the two crystals, H30+ and NH ", should occupy nearly equal amounts of space because they are isoelectronic (having the same number of electrons). 

The scattering of the X-ray beam is directly proportional to the number of electrons an element has. In any X-ray-based technique, elements which are isoelectronic (have the same number of electrons) are indistinguishable to X-rays. This can cause problems in assigning sites in single crystal diffraction, and can lead to additional absences in the powder X-ray diffraction pattern. 

The compounds Br2 and ICl are isoelectronic (have the same number of electrons) and have similar molar masses, yet Br2 melts at —7.2°C and ICl melts at 27.2°C. Explain. 

What we see is that each alkali metal has a single outermost (valence) electron in an s subshell. That commonality gives each element similar properties. For example, they are all extremely reactive metals. Each alkah metal reacts readily, sometimes even explosively, with water. Therefore, none of them is found in nature in pure form. All of these elements form +1 ions—Li, Na, K, etc. The reason for that is that by losing one electron, alkali metals become isoelectronic (having the same number of electrons) as the noble gas elements in the preceding rows. Therefore, like the noble gases, alkali metals are extremely stable entitles. 

The simplest stable heteronuclear molecule is lithium hydride, LiH. Like Hc2, LiH has two nuclei and four electrons. We say that these two molecules are isoelectronic (have the same number of electrons). However, LiH is a stable molecule in the ground state while He2 is not. Figure 20.13 shows the LiH system. We apply the Born-Oppenheimer approximation and place the nuclei on the z axis and place the origin of coordinates at the center of mass of the nuclei. The zero-order electronic Hamiltonian operator for the LiH molecule is (omitting the constant intemuclear repulsion termf ui)... 

Each of the following species will be encountered at some point in this text. They all have the same number of electrons binding the same number of atoms and the same arrangement of bonds they are isoelectronic. Specify which atoms, if any, bear a formal charge in the Lewis stmc-ture given and the net charge for each species. 

Explain in terms of nuclear charge why the K+ ion is smaller than the Cl- ion, though they are isoelectronic (they have the same number of electrons). 

Molecules and ions, like atoms, can be isoelectronic. That is, they can have the same number of electrons. For example, CH4 and NH4+ are isoelectronic. Therefore, they have the same molecular shape. Identify a molecule or ion that is isoelectronic with each of the following species and verify that each pair has the same shape (a) CO 2 (b) 0 ... 

A nitrogen atom can form four bonds only if it loses an electron to become N+ so that it is then isoelectronic with a carbon atom. Isoelectronic atoms or molecules have the same number of valence electrons, arranged in the same way. Thus B, C, and N + are isoelectronic atoms and can each form four bonds. Some examples of isoelectronic molecules are illustrated in Figure 1.15. 

It is interesting to note that both CO and CN are isoelectronic with the N2 molecule. That is, they have the same number and arrangement of electrons as the N2 molecule. However, as we will see later, these species are quite different from N2 in their chemical behavior. The properties of many homonudear and heteronudear molecules and ions are presented in Table 3.1. 

In the literal sense, isoelectronic means having the same number of electrons. (In another sense, not used in the text, it means having the same electron configuration.) We determine the total number of electrons and the electron configuration for each species and make our decisions based on this information. 

Isoelectronic species must have the same number of electrons, and each element has a different atomic number, atoms of different elements cannot be isoelectronic. Two different cations may be isoelectronic, as may two different anions, or an anion and a cation. An example would be two anions (or two cations, or an anion and a cation) that have the electron configuration of a nearby noble gas, such as 02 and F", Na+ and Mg2+, or F and Na+. 

Note that all the ions have 10 electrons that is, they are all isoelectronic with neon. Because they all have the same number of electrons, the only factor that will determine their size will be the nuclear charge — the greater the nuclear charge, the smaller the radius. Therefore, magnesium, with a nuclear charge of +2, has the smallest radius among these ions. 

Isoelectronic means that the species have the same number and arrangement of electrons. 

Referring to two or more molecular entities having the same number and connectivity of atoms (although not necessarily the same elements) as well as the same number of valence electrons. Thus, CO, N2, and NO+ are isoelectronic, as are ketene (CH2=C=0) and diazomethane (CH2=N=N). See Electroneutrality Principle... 

So far the discussion has pertained only to neutral atoms. Simple ions produced from atoms by addition or removal of electrons follow, however, much the same rule. In general, atomic species, whether charged or neutral, have the same electron configuration if they are isoelectronic to each other, that is, if they have the same total number of electrons. Thus Ca++, K+, Cl and S all have the same number of electrons as argon and all have the configuration 3s2 3p6 in the last occupied levels. The only exceptions to this rule may occur... 

Some isoelectronic species of C2B10H12, such as CBnH12-, NB11H12, and their derivatives, are known. Since they have the same number of skeletal atoms and the same bond valence, these compounds are isostructural. 

Isoelectronic Ions Ions which have the same number of electrons are called isoelectronic ions, i.e. O2-, Na+, Al3+ and Ne all have 10 electrons so they are isoelectronic. 

Notice that the delocalization over the nitro group is similar to that over the carboxylate group. In fact, the nitro group is isoelectronic with the carboxylate group, that is, both systems have the same number of electrons. 

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