Which of the following reactions requires the smallest amount of energy to remove a valence electron (e⁻)?

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11ecba2d_1234_886f_a3bf_e3fb10486a4d_MD0008_00 The first ionization energy is the energy required to remove the first, most loosely bound valence electron (e⁻) from a single neutral atom (X) in the gaseous state. The process can be represented generally as: X(g) + energy → X⁺(g) + e⁻ Elements with loosely bound valence electrons have lower first ionization energies (ie, are easier to ionize) than elements with tightly bound valence electrons. On the periodic table, the first ionization energy tends to increase with increasing atomic number moving across a period (row), but it tends to decrease moving down a group (column), with some intermittent exceptions. In this question, each of the given reactions describes the first ionization of an element. Ne and Ar are both noble gases (Group 18) and are further across their respective periods than the halogens F and Cl (Group 17). As a result, each halogen has a lower first ionization energy than its neighboring noble gas on the periodic table. Comparing the halogens, the atoms in the group increase in size moving down the column, which causes the valence electrons in larger halogens to occupy a higher energy level where they are less tightly bound. As a result, removing valence electrons from larger halogens requires less energy than removing valence electrons from smaller halogens. Because halogens have a lower first ionization energy than their neighboring noble gases, and because Cl is larger and farther down the halogen group than F, the first ionization of Cl will require the smallest amount of energy of the given reactions. (Choices A, B, and D) Noble gases such as Ne and Ar have a higher first ionization energy within their respective periods. Cl is larger in size and lower in the halogen column than F, giving F a higher first ionization energy than Cl. Educational objective: The first ionization energy is the energy required to remove the first, most loosely bound valence electron from a neutral atom. The first ionization energy tends to increase with increasing atomic number moving across a period and decrease moving down a group on the periodic table.

Which of the Following Reactions Requires the Smallest Amount of Energy