Ch.9 - Periodic Properties of the Elements

Tro - Chemistry: A Molecular Approach 6th Edition

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Tro 6th Edition

Ch.9 - Periodic Properties of the Elements

Problem 86

Chapter 9, Problem 86

Choose the element with the more negative (more exothermic) electron affinity in each pair. a. Ca or Se b. Ge or S c. Al or O d. Se or I

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Understand the concept of electron affinity: Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gaseous state. A more negative electron affinity indicates a greater tendency to gain an electron, making it more exothermic.

Compare the elements in each pair based on their positions in the periodic table: Generally, electron affinity becomes more negative across a period from left to right and less negative down a group.

For pair a (Ca or Se): Calcium (Ca) is in Group 2, while Selenium (Se) is in Group 16. Elements in Group 16 typically have more negative electron affinities than those in Group 2.

For pair b (Ge or S): Germanium (Ge) is in Group 14, while Sulfur (S) is in Group 16. Elements in Group 16 generally have more negative electron affinities than those in Group 14.

For pair c (Al or O): Aluminum (Al) is in Group 13, while Oxygen (O) is in Group 16. Oxygen, being in Group 16, typically has a more negative electron affinity than Aluminum.

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Key Concepts

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

Electron Affinity

Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gas phase. A more negative electron affinity indicates a greater release of energy, meaning the atom more readily accepts an electron. This property is crucial for understanding how elements interact with electrons and form negative ions.

Periodic Trends

Periodic trends refer to the predictable patterns observed in the properties of elements across the periodic table. For electron affinity, elements on the right side of the table (like halogens) generally have more negative values compared to those on the left (like alkaline earth metals). Understanding these trends helps in predicting the behavior of elements in terms of their electron affinity.

Comparison of Elements

When comparing elements for their electron affinity, it is essential to consider their atomic structure, including the number of valence electrons and their effective nuclear charge. Elements with higher effective nuclear charge tend to have more negative electron affinities because they can attract additional electrons more effectively. This comparison is key to determining which element in each pair has a more exothermic electron affinity.

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Related Practice

Textbook Question

Choose the element with the more negative (more exothermic) electron affinity from each pair. c. P or S

Textbook Question

Choose the more metallic element from each pair. a. Rb or Sn b. P or Sb c. Te or Cl d. O or P

Textbook Question

Arrange these elements in order of increasing metallic character: Fr, Sb, In, S, Ba, Se.

Textbook Question

Choose the more metallic element from each pair. a. As or Sn b. Ca or Ga c. I or Bi d. Br or At

Textbook Question

Consider this set of ionization energies.

IE1 = l000 kJ/mol

IE2 = 2250 kJ/mol

IE3 = 3360 kJ/mol

IE4 = 4560 kJ/mol

IE5 = 7010 kJ/mol

IE6 = 8500 kJ/mol

IE = 27,I00 kJ/mol

To which third-period element do these ionization values belong?

Textbook Question

Choose the element with the more negative (more exothermic) electron affinity from each pair. b. C or F