Beryllium electronic properties

Beryl. 385 Beryllium atomic size, 379 boiling point, 374 bonding capacity, 285 chemistry of, 382 electron configuration. 378 heat of vaporization, 374 ionization energies, 379 occurrence, 384 preparation, 385 properties, 381 structure, 381... 

The metal-donor bonds are predominantly ionic and become more labile for calcium, strontium, and barium compared to beryllium and magnesium. The solubility and stability of the complexes decrease from calcium to barium. The 1 1 adducts of NHCs with BH3 or BF3 (28 and 29) are thermally stable and can be sublimed without decomposition. This is in sharp contrast to the properties of conventional carbenes, which rely on a pronounced metal-to-ligand back donation and are, thus, not suited to forming adducts with electron-poor fragments such as... 

Limited theoretical studies (31, 89) on the electron-deficient beryllium derivatives have been interpreted to imply that extensive Be—Be bonding occurs. If such bonding does occur, the increased bond length observed in the phenylethynyl(methyl)beryllium trimethylamine adduct takes on additional significance since the Be—Be distance in this derivative is increased by almost 0.3 A over that observed in dimethyl-and diethylberyllium. Moreover, if cyclic trimers are formed, then increased metal-metal distances would be likely, thus reducing the probability of stabilization of the bridged system by Be—Be bonding. Additional studies will be required both on structures and of spectroscopic properties of the species to answer these questions. 

The observed abundance of light elements can be used to deduce some of the properties of cosmic rays, which are fast-moving particles such as electrons and protons. The abundances of elements such as lithium, beryllium, and boron suggest that each proton has to... 

The atomic number of beryllium is one less than that of boron, which follows it on the periodic table. Strontium, which is directly below beryllium in period 5 of the periodic table has 34 more protons and 34 more electrons than beryllium. However, the properties of beryllium resemble the much larger strontium more than those of similar-sized boron. 

In the last 20 years, Cl calculations based on a single reference function have lost favor among practitioners. The principal shortcoming of these approaches is that they do not satisfy the property of size-consistency, which means that the Cl energy does not scale properly with the size of the system [112]. It is fairly easy to see why this is so. Consider two beryllium atoms, separated by a distance sufficiently large that the true physical interaction between the atoms vanishes. In a CISD description of this system, contributions to the wave function are excluded in which two electrons on each beryllium atom are in virtual orbitals, since these correspond to quadruply excited determinants and would require a method such as CISDQ or CISDTQ for their inclusion. However, the CISD wave function for a single beryllium atom contains all determinants with two electrons in virtual orbitals. Since Cl methods involve... 

Elements can be divided into groups, or families. Each column of the periodic table in Figure 5 contains one element family. Hydrogen is usually considered separately, so the first element family begins with lithium and sodium in the first column. The second family starts with beryllium and magnesium in the second column, and so on. Just as human family members often have similar looks and traits, members of element families have similar chemical properties because they have the same number of electrons in their outer energy levels. 

Write the electron configurations of beryllium and magnesium. What similarities in their chemical properties can you predict on the basis of their electron configurations ... 

The uniqueness of the beryllium ion s properties can be attributed to its very small size compared to the sizes of the ions of the other alkaline earths. Because of the small size of a beryllium atom, the valence electrons are held very tightly to the nucleus, effectively preventing the formation of a positive ion. 

The alkaline earth metals are somewhat less electropositive and less reactive than the alkali metals. Except for the first member of the family, beryllium, which resembles aluminum (a Group 3A metal) in some respects, the alkaline earth metals have similar chemical properties. Because their ions attain the stable electron configuration of the preceding noble gas, the oxidation number of alkaline earth metals in the combined form is almost always +2. Table 20.5 lists some common properties of these metals. Radium is not included in the table because all radium isotopes are radioactive and it is difficult and expensive to study the chemistry of this Group 2A element. 

The two electrons that fill the 2s orbital in a Be atom would also completely fill the 2s band in solid beryllium. No metallic properties would be expected. 

As the 2s orbitals combine and spread out to form a band, it will overlap with the band generated by the combination of 2p orbitals. So, in solid beryllium (and similarly in other solid elements in Groups I—III (1,2 and 13)), the band generated by combination of atomic orbitals is not a pure 2s band, but one continuous band made by combination of both 2s and 2p orbitals. In consequence, there are unoccupied levels available in the energy band of solid beryllium into which electrons may be excited. This allows the development of metallic properties. 

---