Metallic radii. 178-9 5-block elements

Symbol Ce atomic number 58 atomic weight 140.115 a rare-earth metal a lanthanide series inner-transition /-block element metaUic radius (alpha form) 1.8247A(CN=12) atomic volume 20.696 cm /mol electronic configuration [Xe]4fi5di6s2 common valence states -i-3 and +4 four stable isotopes Ce-140 and Ce-142 are the two major ones, their percent abundances 88.48% and 11.07%, respectively. Ce—138 (0.25%) and Ce—136(0.193%) are minor isotopes several artificial radioactive isotopes including Ce-144, a major fission product (ti 284.5 days), are known. 

The reactivity of the transition metal complexes changes as you go down the Group of the d-block elements. The ionic radius increases due to the fact that the electron cloud around the nucleus gets larger. This leads to weaker... 

Data are given for the p- and first row -block elements. The ionic radius varies with the charge and coordination number of the ion a coordination number of 6 refers to octahedral coordination, and of 4 refers to tetrahedral unless otherwise specified. Data for the heavier -block metals and the lanthanoids and actinoids are listed in Tables 23.1 and 25.1. 

Symbol Lu atomic number 71 atomic weight 174.97 a lanthanide series element an /-block inner-transition metal electron configuration [Xe]4/i45di6s2 valence -1-3 atomic radius (coordination number 12) 1.7349A ionic radius (Lu3+) 0.85A two naturally-occurring isotopes Lu-176 (97.1%) and Lu-175(2.59%) Lu-172 is radioactive with a half-life of 4xl0i° years (beta-emission) several artificial isotopes known, that have mass numbers 155, 156, 167—174, 177—180. 

Towards the end of each of the three series which constitute the d block, we observe a marked increase in radius. For reasons discussed in more detail in Section 7.5, the filled nd subshell tends to weaken the bonding in metallic elemental substances, leading to longer internuclear distances. 

The electronegativity increases in periods as eff increases and atomic radius decreases. In the main groups, the electronegativity decreases as the atomic radius inCTeases and eff decreases. In the secondary groups, this property is irregular. In elanents in the d-block and f-block in lower oxidation states (where ns or (n-1) d ns electrons participate only) the electropositive (metallic) character prevails. This character is less pronounced than that of the typical metallic elements because of the contraction of the atomic orbitals. In higher oxidation states these elements have a weak electropositive character. 

It turns out that for the s and p block metals, a simple model, namely, thejdlium model provides useful insight. In this model, the discrete nature of the ionic lattice is replaced with a smeared out uniform positive background exactly equal to that of the valence electron gas. In jellium, each element is completely specified by just the electron density n = N/V, where N is the number of electrons in the crystal and V is its volume. Often, the electron density is given in terms of the so-called Wigner-Seitz radius, tj, where tg = which corresponds to the spherical... 

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