Passage
The alkaline-earth metals are a highly reactive family of metals occupying Group 2 (IIA) of the periodic table. In their elemental form, the alkaline-earth metals have a shiny, silvery-white to slightly yellowish appearance. The alkaline-earth metals exhibit some similarities to the chemistry of the alkali metals (Group 1) but are a little less reactive.Atoms of the alkaline-earth metals (M) have only two valence electrons and a low first and second ionization energy. Consequently, these metals readily lose both electrons to produce cations with a +2 charge (M +2 ) during reactions with nonmetals. As a result, the alkaline-earth metals do not exist in their elemental metallic form in nature. Instead, the Group 2 elements are found primarily as metal oxides, which form by reacting oxygen (Reaction 1).

Similarly, elemental samples of alkaline-earth metals will react with elemental halogens (X 2 ) to form metal halides (Reaction 2), all of which are ionic except for BeCl 2 .

Except for beryllium, the alkaline-earth metals react with water to produce very basic metal hydroxide solutions and hydrogen gas (Reaction 3).

The most difficult alkaline-earth metal to study is radium, because it is a rare radioactive element that is produced from the nuclear decay of uranium. The most common natural isotope, radium-226, has a half-life of 1,600 years and decays by alpha emission into radon-222 (Reaction 4).

-When comparing atoms across the same row of the periodic table, which of the following groups will contain the atom with the lowest second ionization energy?

Question

Passage
The alkaline-earth metals are a highly reactive family of metals occupying Group 2 (IIA) of the periodic table.  In their elemental form, the alkaline-earth metals have a shiny, silvery-white to slightly yellowish appearance.  The alkaline-earth metals exhibit some similarities to the chemistry of the alkali metals (Group 1) but are a little less reactive.Atoms of the alkaline-earth metals (M) have only two valence electrons and a low first and second ionization energy.  Consequently, these metals readily lose both electrons to produce cations with a +2 charge (M +2 ) during reactions with nonmetals.  As a result, the alkaline-earth metals do not exist in their elemental metallic form in nature.  Instead, the Group 2 elements are found primarily as metal oxides, which form by reacting oxygen (Reaction 1).
  
Similarly, elemental samples of alkaline-earth metals will react with elemental halogens (X 2 ) to form metal halides (Reaction 2), all of which are ionic except for BeCl 2 .
  
Except for beryllium, the alkaline-earth metals react with water to produce very basic metal hydroxide solutions and hydrogen gas (Reaction 3).
  
The most difficult alkaline-earth metal to study is radium, because it is a rare radioactive element that is produced from the nuclear decay of uranium.  The most common natural isotope, radium-226, has a half-life of 1,600 years and decays by alpha emission into radon-222 (Reaction 4).
 
-When comparing atoms across the same row of the periodic table, which of the following groups will contain the atom with the lowest second ionization energy?

Quizplus · Accepted Answer

11ecba2d_11e4_e177_a3bf_03254ee9b068_MD0008_00 Ionization energy is the energy required to remove an electron (e⁻) from an atom or ion (measured in the gas state). The first ionization energy refers to the removal of the first electron from a neutral atom of an element (X): X + energy → X⁺ + e⁻ The second ionization energy refers to the removal of a second electron: X⁺ + energy → X⁺² + e⁻ Loosely bound electrons (valence electrons) are removed first before any core electrons. Accordingly, removing a core electron takes more energy than does removing a valence electron. On the periodic table, metals generally have a lower first ionization energy than nonmetals, and first ionization energies tend to increase across a row and decrease down a column. The same is true for the second ionization energy except when the second electron being removed is not a valence electron. If comparing elements in period (row) three, the nonmetals Si (Group 14) and S (Group 16) are farther to the right in the period, and both have a higher second ionization energy than Mg. However, the second ionization energy of Na (Group 1) is much higher than that of Mg (Group 2) because Na has only one valence electron and removing a second electron from Na requires the loss of a core electron. The availability of a second valence electron gives Mg (Group 2) the lowest second ionization energy. (Choice A) Group 1 metals have only one valence electron, and a second ionization requires the loss of a tightly bound core electron. (Choices C and D) When removing valence electrons, nonmetals generally have a higher second ionization energy than metals; among metals, ionization energies tend to increase from left to right across a period. Educational objective: The second ionization energy is the energy required to remove the second of two electrons from an atom. The second ionization energy tends to increase across a period and to decrease down a group; however, ionizations involving core electrons are higher energy than those involving valence electrons.