Ch.9 - Periodic Properties of the Elements

Problem 85b

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Chapter 9, Problem 85b

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

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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 accept an electron.

Consider the periodic trend: Electron affinity generally becomes more negative across a period from left to right due to increasing nuclear charge, which attracts electrons more strongly.

Identify the position of the elements in the periodic table: Carbon (C) is in group 14 and period 2, while Fluorine (F) is in group 17 and period 2.

Compare the elements based on their positions: Since both elements are in the same period, the trend suggests that the element further to the right (Fluorine) will have a more negative electron affinity.

Conclude based on the trend: Fluorine, being to the right of Carbon in the same period, is expected to have a more negative (more exothermic) electron affinity.

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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 that the process is more exothermic, meaning energy is released when the atom gains an electron. This property is crucial for understanding how easily an atom can accept an electron and form an anion.

Trends in Electron Affinity

Electron affinity varies across the periodic table, generally increasing (becoming more negative) from left to right and decreasing from top to bottom. This trend is due to the increasing nuclear charge and decreasing atomic radius, which enhance the attraction between the nucleus and the added electron. Understanding these trends helps predict the electron affinity of different elements.

Comparison of Carbon and Fluorine

When comparing carbon (C) and fluorine (F), fluorine has a significantly more negative electron affinity than carbon. This is because fluorine, being more electronegative, has a stronger tendency to attract additional electrons, resulting in a more exothermic process. This comparison illustrates the importance of electronegativity in determining electron affinity.

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Related Practice

Textbook Question

Arrange these elements in order of increasing first ionization energy: Si, F, In, N.

For each element, predict where the "jump" occurs for successive ionization energies. (For example, does the jump occur between the first and second ionization energies, the second and third, the third and fourth, and so on?) a. B b. Na C. P d. S

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. c. P or S

Textbook Question

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

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