Atomic radius Period 2 elements

The electron configuration or orbital diagram of an atom of an element can be deduced from its position in the periodic table. Beyond that, position in the table can be used to predict (Section 6.8) the relative sizes of atoms and ions (atomic radius, ionic radius) and the relative tendencies of atoms to give up or acquire electrons (ionization energy, electronegativity). 

Because carbon stands at the head of its group, we expect it to differ from the other members of the group. In fact, the differences between the element at the head of the group and the other elements are more pronounced in Group 14/IV than anywhere else in the periodic table. Some of the differences between carbon and silicon stem from the smaller atomic radius of carbon, which explains the wide occurrence of C=C and G=Q double bonds relative to the rarity of Si=Si and Si=0 double bonds. Silicon atoms are too large for the side-by-side overlap of p-orbitals necessary for -it-bonds to form between them. Carbon dioxide, which consists of discrete 0=C=0 molecules, is a gas that we exhale. Silicon dioxide (silica), which consists of networks of —O—Si- O - groups, is a mineral that we stand on. 

The Periodic Table forms one of the most remarkable, concise, and valuable tabulations of data in science. Its power lies in the regularities that it reveals, thus, in some respects, it has the same role as the SOM. Construct a SOM in which the input consists of a few properties of some elements, such as electronegativity, atomic mass, atomic radius, and electron affinity. Does the completed map show the kind of clustering of elements that you would expect What is the effect of varying the weight given to the different molecular properties that you are using ... 

Consider the element with atomic number 116 in Group 6A. Even though it has not been isolated, its atomic radius is expected to be somewhat larger than that of Po (1.68 A), probably about 1.9 - 2.0 A, since it lies just below Po on the periodic table. Its outer electrons would lie in the n=l shell, which would be further away from the nucleus than Po s outermost electrons in the n=6 shell. 

How does the atomic radius affect the ionization energies of the elements in a family on the periodic table ... 

Figure 4.14. Atomic dimensions of the elements. In this scheme each element, represented in its position of the Periodic Table, is indicated by a circle the diameter of which is roughly proportional to the atomic radius for coordination 12 (Teatum etal. 1968).

A. PERIODS The 7 horizontal rows, called periods, contain the elements with increasing atomic numbers. Period 1 has the elements with one shell. Period 2 has the elements with two shells. Period 3 has the elements with three shells, etc. The first period contains 2 elements the second and third, eight elements the fourth and fifth, ei teen elements. In a period, the atomic radius generally decreases from Group I to Group VII. 

In addition to reactivity, another property that varies across the table is atomic radius, or the geometric size (not the mass) of the atoms. As you move down or to the right on the periodic table, elements have both more protons and more electrons. However, only as you move down the table do the added electrons occupy higher energy levels. Therefore, the following occurs ... 

FIGURE 5.1 Agraph of atomic radius in picometers (pm) versus atomic number shows a rise-and-fall pattern of periodicity. The maxima occur for atoms of group 1A elements (Li, Na, K, Rb, Cs, Fr) the minima occur for atoms of the group 7A elements. Accurate data are not available for the group 8A elements. 

One of the many periodic properties of the elements that can be explained by electron configurations is size, or atomic radius. You might wonder, though, how we can talk about a definite "size" for an atom, having said in Section 5.8 that the electron clouds around atoms have no specific boundaries. What s usually done is to define an atom s radius as being half the distance between the nuclei of two identical atoms when they are bonded together. In the Cl2 molecule, for example, the distance between the two chlorine nuclei is 198 pm in diamond (elemental carbon), the distance between two carbon nuclei is 154 pm. Thus, we say that the atomic radius of chlorine is half the Cl-Cl distance, or 99 pm, and the atomic radius of carbon is half the C-C distance, or 77 pm. 

Use the Interactive Periodic Table (eChapter 5.1) to compare the atomic radius and the ionic radius of the elements in group 2A. How does the ionic radius compare to the atomic radius Explain this trend. 

The properties of the elements of the sixth period are influenced by lanthanide contraction a gradual decrease of the atomic radius with increasing atomic number from La to Lu. The elements of groups 5 to 11 for the fifth and sixth periods have comparable stmctural parameters. For instance, Nb and Ta, as well as the pair Mo and W, have very similar ionic radii, when they have the same oxidation number. As a result, it is very difficult to separate Nb and Ta, and it is also not easy to separate Mo and W. Similarly, Ag and Au have nearly the same atomic radius, 144 pm. Recent studies of the coordination compounds of Ag(I) and Au(I) indicate that the covalent radius of Au is even shorter than that of Ag by about 8 pm. In elementary textbooks the phenomenon of lanthanide contraction is attributed to incomplete shielding of the nucleus by the diffuse 4f inner subshell. Recent theoretical calculations conclude that lanthanide contraction is the result of both the shielding effect of the 4f electrons and relativistic effects, with the latter making about 30% contribution. 

Germanium is disposed in the center of group 14 of the periodic table of the elements. Increased stability of divalent species, which is more pronounced for tin and lead, begins from this element. The main characteristics of these atoms, such as atomic radius, energy of ionization, electron affinity, electronegativity and other features, are presented in parallel in a review12. 

Metals, nonmetals, and atomic radius Elements in the periodic table are divided into the two broad categories of metals and nonmetals with a jagged line separating the two as shown in the figure. 

Because of the arrangement of elements on the periodic table, there are several patterns that can be seen between the elements. These patterns, or periodic trends, can be observed for atomic radius, ionic radii, ionization energies, electron affinities, and electronegativities. You should be familiar with the periodic and group trends for each of these. 

Your understanding of periodic trends such as atomic radius and ionization energy will help you identify some unknown elements in the Chemistry Course Challenge at the end of this book. 

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