Periodic Table trends down Groups

Electron energy calculations now offer a coherent explanation of trends observed both across and down the periodic table and the grouping and overlaps observed in structure maps. Of particular importance are the marked changes that occur on moving to elements of higher atomic number, which means that some of the earlier assumptions concerning similarities of behaviour for compounds of the 3d, 4d, and 5d elements (Kaufman and Bernstein 1970) have had to be revised. Quantum... 

One important characteristic of atoms is their size. The measurement of atomic size is sometimes complicated. The results of these measurements are summarized in Figure 6.20. There are two ways to explore trends in the periodic table, within a group and within a period. As we go down a group, we observe an increase in atomic size. As we go across a period, we observe a decrease. An easy way to remember this trend is to draw what look like x, y coordinate axes at the bottom left of the periodic table. An increase in either the x or y direction on these axes corresponds to a decrease in atomic size. How do we understand this trend ... 

The binary borides (p. 145), carbides (p. 299), and nitrides (p. 418) have already been discussed. Suffice it to note here that the chromium atom is too small to allow the ready insertion of carbon into its lattice, and its carbide is consequently more reactive than those of its predecessors. As for the hydrides, only CrH is known which is consistent with the general trend in this part of the periodic table that hydrides become less stable across the d block and down each group. 

The radii of cations and anions derived from atoms of the main-group elements are shown at the bottom of Figure 6.13. The trends referred to previously for atomic radii are dearly visible with ionic radius as well. Notice, for example, that ionic radius increases moving down a group in the periodic table. Moreover the radii of both cations (left) and anions (right) decrease from left to right across a period. 

As shown in Table 4.55, this quantity increases going down the periodic column in each group, a trend that is known to hold generally throughout the d-block elements. This d-block trend is in contrast to the corresponding main-group trend for bond strengths to diminish down a periodic column. 

Periodic trends in ionization energy are linked to trends involving the reactivity of metals. In general, the chemical reactivity of metals increases down a group and decreases across a period. These trends, as well as a further trend from metallic to non-metallic properties across a period, and increasing metallic properties down a group, are shown in Table 3.1. 

What general trends are noticeable down the groups of the Periodic Table in the values of (a) the first ionization energies, (b) the first electron attachment energies and (c) the covalent radii of the elements ... 

The general trends across periods and down groups of the Periodic Table are influenced by relativistic effects, which become more serious in the heavier elements (Z > 55). This can only be dealt with here in a brief manner. 

True, except for the group 18 noble gas elements, which are not assigned an electronegativity number. The trend is that electronegativity decreases with an increasing number of shells down any one atomic group (vertical column) of the periodic table. 

Use the Interactive Periodic Table in eChapter 5.15 to determine the trend in atomic radius as you move across a period and as you move down a group. Explain the factors that account for these trends. 

The group 4A elements exemplify the increase in metallic character down a group in the periodic table Carbon is a nonmetal silicon and germanium are semimetals and tin and lead are metals. The usual periodic trends in atomic size, ionization energy, and electronegativity are evident in the data of Table 19.4. 

Sketch an outline of the periodic table. Add labels and arrows to indicate what you think are the trends for ionic size (radius) across a period and down a group. 

The metallic character of the elements in the periodic table, and the acid-base properties of their oxides, show a distinct trend across periods and down groups. Infer what this trend is. 

In other words, state what you think happens to the acid-base properties of oxides as you go across a period and down a group. Make a quick sketch of the periodic table to illustrate this trend. Flow would you describe the acid-base properties of the metalloids (Use your knowledge of the physical properties of the metalloids to help you make your inference.)... 

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