Transition elements, electronic configurations

Symbol Am Atomic Number 95 Atomic Weight 243.0614 an inner-transition, actinide series, radioactive man-made element electron configuration ... 

Symbol Ir atomic number 77 atomic weight 192.22 a Group VIII (Group 8) transition metal electron configuration [Xe]4/i45d 6s2 common valence states -1-3 and +4 valence states 0, -i-l, +2, -i-5 and -i-6 are known two natural isotopes, lr-191 (37.30%) and Ir-193 (62.70%) The element has 28 radioisotopes, ranging in masses from 170 to 198. 

Symbol Lr atomic number 103 atomic weight 262 a transuranium inner-transition actinide series element a synthetic radioactive element electron configuration [RnjTs b/ Sdi valence +3 six isotopes of masses 255 to 260 have been synthesized longest-lived known isotope Lr-260 has half-life of 3 minutes. 

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. 

Symbol Pa atomic number 91 atomic weight 231.04 an actinide series radioactive element an inner-transition metal electron configuration [Rn]5/26di7s2 valence states +4 and +5 atomic radius 1.63A (for coordination number 12) twenty-two isotopes are known in the mass range 215-218,... 

Polyatomic molecules cover such a wide range of different types that it is not possible here to discuss the MOs and electron configurations of more than a very few. The molecules that we shall discuss are those of the general type AFI2, where A is a first-row element, formaldehyde (FI2CO), benzene and some regular octahedral transition metal complexes. 

Titanium is the first member of the t7-block transition elements. Its electron configuration is [Ar] and successive ionisation potentials are 6.83,... 

The unique nature of the electronic configuration of copper, which contributes to its high electrical and heat conductivity, also provides chemical properties intermediate between transition and 18-sheU elements. Copper can give up the 4s electron to form the copper(I) ion [17493-86-6] or release an additional electron from the >d orbitals to form the copper(Il) ion [15158-11-9]. 

As you can see from Figure 6.9, the electron configurations of several elements (marked ) differ slightly from those predicted. In every case, the difference involves a shift of one or, at the most, two electrons from one sublevel to another of very similar energy. For example, in the first transition series, two elements, chromium and copper, have an extra electron in the 3d as compared with the 4s orbital. 

There are two immediate questions we ask about the transition elements once we know where they are in the periodic table (1) Why do we consider these elements together (2) What is special about their properties These questions are closely related because they both depend upon the electron configurations of the atoms. What, then, is the electron configuration we might expect for these elements ... 

Table 22-1. the electron configurations of the fourth-row transition ELEMENTS... 

Make an electron configuration table like Table 22-1 for the fifth-row transition elements— yttrium (Z = 39) through cadmium (Z = 48). In elements 41 through 45, one of the 5s electrons moves over to a 4d orbital. In element 46, two electrons do this. 

According to this assignment the differentiating electron, that is, the final electron to enter the atom of lutetium, wss seen as an f electron. This suggested that lutetium should be the final element in the first row of the rare earth elements, in which f electrons are progressively filled, and not a transition element as had been believed by the chemists. As a result of more recent spectroscopic experiments the configuration of ytterbium has been altered to (27)... 

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