The As ¬ As bond length in elemental arsenic is 2.48 Å. The Cl ¬ Cl bond length in Cl2 is 1.99 Å. (a) Based on these data, what is the predicted As ¬ Cl bond length in arsenic trichlo- ride, AsCl₃, in which each of the three Cl atoms is bonded to the As atom?

The following observations are made about two hypothetical elements A and B: The A—A and B—B bond lengths in the elemental forms of A and B are 2.36 and 1.94 Å, respectively. A and B react to form the binary compound AB2, which has a linear structure (that is, ∠B-A-B=180°). Based on these statements, predict the separation between the two B nuclei in a molecule of AB2.

The As ¬ As bond length in elemental arsenic is 2.48 Å. The Cl ¬ Cl bond length in Cl2 is 1.99 Å. (b) What bond length is predicted for AsCl₃, using the atomic radii in Figure 7.7?

Elements in group 7A in the periodic table are called the halogens; elements in group 6A are called the chalcogens. (a) What is the most common oxidation state of the chalcogens compared to the halogens?

(c) Will the lithium cobalt oxide cathode expand or contract as lithium ions are inserted?

(d) Lithium is not nearly as abundant as sodium. If sodium ion batteries were developed that function in the same manner as lithium ion batteries, do you think 'sodium cobalt oxide' would still work as the electrode material? Explain.

Explain the variation in the ionization energies of carbon, as displayed in this graph:

The ionic substance strontium oxide, SrO, forms from the reaction of strontium metal with molecular oxygen. The arrangement of the ions in solid SrO is analogous to that in solid NaCl: (a) Write a balanced equation for the formation of SrO(s) from its elements.

The ionic substance strontium oxide, SrO, forms from the reaction of strontium metal with molecular oxygen. The arrangement of the ions in solid SrO is analogous to that in solid NaCl:

(b) Based on the ionic radii in Figure 7.8, predict the length of the side of the cube in the figure (the distance from the center of an atom at one corner to the center of an atom at a neighboring corner).

The ionic substance strontium oxide, SrO, forms from the reaction of strontium metal with molecular oxygen. The arrangement of the ions in solid SrO is analogous to that in solid NaCl:

(c) The density of SrO is 5.10 g>cm3. Given your answer to part (b), how many formula units of SrO are contained in the cube shown here?

In the chemical process called electron transfer, an electron is transferred from one atom or molecule to another. (We will talk about electron transfer extensively in Chapter 20.) A simple electron transfer reaction is A(g) + A(g) → A⁺(g) + A^-(g) For a representative nonmetal such as chlorine, is this process exothermic?

(a) Use orbital diagrams to illustrate what happens when an oxygen atom gains two electrons

Identify two ions that have the following ground-state electron configurations: (a) [Ar]

Identify two ions that have the following ground-state electron configurations: (b) [Ar]3d⁵

Identify two ions that have the following ground-state electron configurations: (c) [Kr]5s²4d¹⁰

Which of the following chemical equations is connected to the definitions of (a) the first ionization energy of oxygen (i) O1g2 + e-¡O-1g2 (ii) O1g2¡O+1g2 + e- (iii) O1g2 + 2 e-¡O2-1g2 (iv) O1g2¡O2+1g2 + 2 e- (v) O+1g2¡O2+1g2 + e-

Hydrogen is an unusual element because it behaves in some ways like the alkali metal elements and in other ways like nonmetals. Its properties can be explained in part by its electron configuration and by the values for its ionization energy and electron affinity. (a) Explain why the electron affinity of hydrogen is much closer to the values for the alkali elements than for the halogens.

The first ionization energy of the oxygen molecule is the energy required for the following process: O21g2¡O2 +1g2 + e- The energy needed for this process is 1175 kJ>mol, very similar to the first ionization energy of Xe. Would you expect O2 to react with F2? If so, suggest a product or products of this reaction.

It is possible to define metallic character as we do in this book and base it on the reactivity of the element and the ease with which it loses electrons. Alternatively, one could measure how well electricity is conducted by each of the elements to determine how 'metallic' the elements are. On the basis of conductivity, there is not much of a trend in the periodic table: Silver is the most conductive metal, and manganese the least. Look up the first ionization energies of silver and manganese; which of these two elements would you call more metallic based on the way we define it in this book?

Which of the following is the expected product of the reaction of K(s) and H₂(g)? (i) KH(s), (ii) K₂H(s), (iii) KH₂(s), (iv) K₂H₂(s), or (v) K(s) and H₂(g) will not react with one another.

A historian discovers a nineteenth-century notebook in which some observations, dated 1822, were recorded on a substance thought to be a new element. Here are some of the data recorded in the notebook: 'Ductile, silver-white, metallic looking. Softer than lead. Unaffected by water. Stable in air. Melting point: 153 °C. Density: 7.3 g>cm3. Electrical conductivity: 20% that of copper. Hardness: About 1% as hard as iron. When 4.20 g of the unknown is heated in an excess of oxygen, 5.08 g of a white solid is formed. The solid could be sublimed by heating to over 800 °C.' (a) Using information in the text and the CRC Handbook of Chemistry and Physics, and making allowances for possible variations in numbers from current values, identify the element reported.

We will see in Chapter 12 that semiconductors are materials that conduct electricity better than nonmetals but not as well as metals. The only two elements in the periodic table that are technologically useful semiconductors are silicon and germanium. Integrated circuits in computer chips today are based on silicon. Compound semiconductors are also used in the electronics industry. Examples are gallium arsenide, GaAs; gallium phosphide, GaP; cadmium sulfide, CdS; and cadmium selenide, CdSe. (a) What is the relationship between the compound semiconductors' compositions and the positions of their elements on the periodic table relative to Si and Ge?

We will see in Chapter 12 that semiconductors are materials that conduct electricity better than nonmetals but not as well as metals. The only two elements in the periodic table that are technologically useful semiconductors are silicon and germanium. Integrated circuits in computer chips today are based on silicon. Compound semiconductors are also used in the electronics industry. Examples are gallium arsenide, GaAs; gallium phosphide, GaP; cadmium sulfide, CdS; and cadmium selenide, CdSe. (b) Workers in the semiconductor industry refer to 'II–VI' and 'III–V' materials, using Roman numerals. Can you identify which compound semiconductors are II–VI and which are III–V? (c) Suggest other compositions of compound semiconductors based on the positions of their elements in the periodic table.

Moseley established the concept of atomic number by studying X rays emitted by the elements. The X rays emitted by some of the elements have the following wavelengths: Element Wavelength (pm) Ne 1461 Ca 335.8 Zn 143.5 Zr 78.6 Sn 49.1 (a) Calculate the frequency, n, of the X rays emitted by each of the elements, in Hz.

Moseley established the concept of atomic number by studying X rays emitted by the elements. The X rays emitted by some of the elements have the following wavelengths: Element Wavelength (pm) Ne 1461 Ca 335.8 Zn 143.5 Zr 78.6 Sn 49.1 (b) Plot the square root of n versus the atomic number of the element. What do you observe about the plot? (e) A particular element emits X rays with a wavelength of 98.0 pm. What element do you think it is?

Moseley established the concept of atomic number by studying X rays emitted by the elements. The X rays emitted by some of the elements have the following wavelengths: Element Wavelength (pm) Ne 1461 Ca 335.8 Zn 143.5 Zr 78.6 Sn 49.1 (d) Use the result from part (b) to predict the X-ray wavelength emitted by iron.