Beryllium ionization energy

LITHIUM AND BERYLLIUM IONIZATION ENERGIES AND ATOMIC SIZES... 

Lithium and beryllium ionization energies and atomic sizes... 

If you look carefully at Figure 6.15, you will note a few exceptions to the general trends referred to above and illustrated in Example 6.11. For example, the ionization energy of B (801 kj/mol) is less than that of Be (900 kj/mol). This happens because the electron removed from the boron atom comes from the 2p as opposed to the 2s sublevel for beryllium. Because 2p is higher in energy than 2s, it is not too surprising that less energy is required to remove an electron from that sublevel. 

The electron configuration for lithium is ls 2s1 and for beryllium it is ls 2s. Estimate the approximate ionization energies to remove first one, then a second, electron. Explain your estimates. 

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... 

Self-Test 1.14A Account for the slight decrease in first ionization energy between beryllium and boron. 

Metallic elements with low ionization energies commonly form basic ionic oxides. Elements with intermediate ionization energies, such as beryllium, boron, aluminum, and the metalloids, form amphoteric oxides. These oxides do not react with or dissolve in water, but they do dissolve in both acidic and basic solutions. 

The valence electron configuration of the atoms of the Group 2 elements is ns1. The second ionization energy is low enough to be recovered from the lattice enthalpy (Fig. 14.18). Flence, the Group 2 elements occur with an oxidation number of +2, as the cation M2+, in all their compounds. Apart from a tendency toward nonmetallic character in beryllium, the elements have all the chemical characteristics of metals, such as forming basic oxides and hydroxides. 

Beryllium behaves differently from the other s-block elements because the fi = 2 orbitals are more compact than orbitals with higher principal quantum number. The first ionization energy of beryllium, 899 kJ/mol, is comparable with those of nonmetals, so beryllium does not form compounds that are clearly ionic. 

The first three ionization energies (f, I2, and I3) for beryllium and neon are given in the following table ... 

I. Note that in the case of both beryllium and neon, ionization energies increase as one moves from f to I2 to I3. 

I Beryllium There is generally not enough energy available in chemical reactions to remove inner electrons, as noted by the significantly higher third ionization energy. 

Divalent beryllium honds through two equivalent sp, or (Sgonal, hybrids. The appropriate ionization energy therefore is not that of ground state beryllium, ls2 2. hut an average of those energies necessary to remove electrons from the promoted, valence state ... 

Metallic elements with low ionization energies commonly form ionic oxides. As remarked in Section 10.1, the oxide ion is a strong base, so the oxides of most of these metals form basic solutions in water. Magnesium is an exception because its oxide, MgO, is insoluble in water. However, even this oxide reacts with acids, so it is regarded as basic. Elements with intermediate ionization energies, such as beryllium, boron, aluminum, and the metalloids, form amphoteric oxides. These oxides do not react with water, but they do dissolve in both acidic and basic solutions. 

In Fig. 12.35 we see that there are some discontinuities in ionization energy in going across a period. For example, discontinuities occur in Period 2, in going from beryllium to boron and from nitrogen to oxygen. These exceptions to the normal trend can be explained in terms of how electron repulsions depend on the electron configuration. We will discuss the elements in Period 2 individually to further develop the concept of shielding. 

Similar trends are observed in the second ionization energies, but they are shifted higher in atomic number by one unit (see Fig. 5.24). Thus, IE2 is large for lithium (because Li has a filled Is shell), but relatively small for beryllium (because Be has a single electron in the outermost 2s orbital). 

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