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Ch.7 - Periodic Properties of the Elements
All textbooksBrown 14th EditionCh.7 - Periodic Properties of the ElementsProblem 73
Chapter 7, Problem 73

Compare the elements bromine and chlorine with respect to the following properties: (a) electron configuration (b) most common ionic charge (c) first ionization energy (d) reactivity toward water (e) electron affinity (f) atomic radius

Verified step by step guidance
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Step 1: Electron Configuration - Write the electron configurations for bromine (Br) and chlorine (Cl). Chlorine has the electron configuration [Ne] 3s² 3p⁵, while bromine has [Ar] 4s² 3d¹⁰ 4p⁵. Notice the similarities and differences in their valence electron configurations.
Step 2: Most Common Ionic Charge - Determine the most common ionic charge for each element. Both chlorine and bromine typically form anions with a -1 charge, as they gain one electron to achieve a noble gas configuration.
Step 3: First Ionization Energy - Compare the first ionization energies of chlorine and bromine. Ionization energy generally decreases down a group, so chlorine, being higher up in the periodic table, has a higher ionization energy than bromine.
Step 4: Reactivity Toward Water - Discuss the reactivity of chlorine and bromine with water. Chlorine reacts with water to form hypochlorous acid and hydrochloric acid, while bromine is less reactive with water under normal conditions.
Step 5: Electron Affinity and Atomic Radius - Compare the electron affinities and atomic radii. Chlorine has a higher electron affinity than bromine, meaning it more readily accepts an electron. In terms of atomic radius, bromine is larger than chlorine due to its position lower in the periodic table.

Key Concepts

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

Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals. For bromine (Br) and chlorine (Cl), their configurations are [Ar] 4s² 3p⁵ and [Ne] 3s² 3p⁵, respectively. This arrangement influences their chemical properties, including reactivity and ionization energy, as it determines how easily they can gain or lose electrons.
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Electron Configuration Example

Ionization Energy

Ionization energy is the energy required to remove an electron from an atom in its gaseous state. Chlorine has a higher ionization energy than bromine due to its smaller atomic radius and greater effective nuclear charge, making it more difficult to remove an electron. This property is crucial for understanding the elements' reactivity and their tendency to form ions.
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Reactivity with Water

Reactivity with water refers to how readily an element reacts with water to form hydroxides or acids. Chlorine is more reactive than bromine, readily forming hydrochloric acid when reacting with water, while bromine reacts less vigorously. This difference in reactivity is linked to their positions in the periodic table and their respective electron configurations.
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Related Practice
Textbook Question

(a) As described in Section 7.7, the alkali metals react with hydrogen to form hydrides and react with halogens to form halides. Compare the roles of hydrogen and halogens in these reactions. Write balanced equations for the reaction of fluorine with calcium and for the reaction of hydrogen with calcium. (b) What is the oxidation number and electron configuration of calcium in each product?

Textbook Question

Potassium and hydrogen react to form the ionic compound potassium hydride. (b) Use data in Figures 7.10 and 7.12 to determine the energy change in kJ/mol for the following two reactions:

K(g) + H(g) → K+(g) + H-(g)

K(g) + H(g) → K-(g) + H+(g)

Textbook Question

Little is known about the properties of astatine, At, because of its rarity and high radioactivity. Nevertheless, it is possible for us to make many predictions about its properties. (a) Do you expect the element to be a gas, liquid, or solid at room temperature?

Textbook Question

Little is known about the properties of astatine, At, because of its rarity and high radioactivity. Nevertheless, it is possible for us to make many predictions about its properties. (b) Would you expect At to be a metal, nonmetal, or metalloid? Explain.

Textbook Question

Little is known about the properties of astatine, At, because of its rarity and high radioactivity. Nevertheless, it is possible for us to make many predictions about its properties. (c) What is the chemical formula of the compound it forms with Na?