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Ch.7 - Periodic Properties of the Elements
Chapter 7, Problem 24

The experimental Bi─I bond length in bismuth triiodide, Bil3, is 2.81 Å. Based on this value and the data in Figure 7.7, predict the atomic radius of Bi.

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1
Identify the type of bond in bismuth triiodide (BiI₃) and note that the Bi─I bond length is given as 2.81 Å.
Understand that the bond length in a diatomic molecule is approximately the sum of the atomic radii of the two bonded atoms.
Refer to Figure 7.7 for the atomic radius of iodine (I).
Use the formula: Bond length = Atomic radius of Bi + Atomic radius of I, and rearrange it to find the atomic radius of Bi: Atomic radius of Bi = Bond length - Atomic radius of I.
Substitute the given bond length and the atomic radius of iodine from Figure 7.7 into the equation to calculate the atomic radius of Bi.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Bond Length

Bond length is the average distance between the nuclei of two bonded atoms. It is influenced by the size of the atoms and the type of bond (single, double, etc.). In the case of Bi─I in bismuth triiodide (BiI3), the bond length can provide insights into the atomic radius of bismuth, as it reflects the spatial arrangement of the atoms in the molecule.
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Atomic Radius

The atomic radius is a measure of the size of an atom, typically defined as the distance from the nucleus to the outermost electron shell. Atomic radii can vary based on the type of bonding and the surrounding environment. Understanding the atomic radius is crucial for predicting how atoms will interact in compounds, such as in the case of bismuth in BiI3.
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Periodic Trends

Periodic trends refer to the predictable patterns in the properties of elements as you move across or down the periodic table. For instance, atomic radius generally decreases across a period due to increased nuclear charge and increases down a group due to added electron shells. Recognizing these trends helps in estimating atomic sizes and understanding the behavior of elements in compounds.
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Related Practice
Textbook Question

Tungsten has the highest melting point of any metal in the periodic table: 3422°C. The distance between the centers of W atoms in tungsten metal is 2.74 Å. c. If you put tungsten metal under high pressure, predict what would happen to the distance between W atoms.

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Textbook Question

Which of the following statements about the bonding atomic radii in Figure 7.7 is incorrect? (i) For a given period, the radii of the representative elements generally decrease from left to right across a period. (ii) The radii of the representative elements for the n = 3 period are all larger than those of the corresponding elements in the n = 2 period. (iii) For most of the representative elements, the change in radius from the n = 2 to the n = 3 period is greater than the change in radius from n = 3 to n = 4. (iv) The radii of the transition elements generally increase moving from left to right within a period. (v) The large radii of the Group 1 elements are due to their relatively small effective nuclear charges.

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Textbook Question

Estimate the As¬I bond length from the data in Figure 7.7 and compare your value to the experimental As ¬I bond length in arsenic triiodide, AsI3, 2.55 Å.

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Textbook Question

Using only the periodic table, arrange each set of atoms in order from largest to smallest: (c) F, O, N.

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Textbook Question

Using only the periodic table, arrange each set of atoms in order of increasing radius. b. In, Sn, As

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Textbook Question

Identify each statement as true or false: (a) Cations are larger than their corresponding neutral atoms.

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