Passage
The alkali metals are a highly reactive family of metals occupying Group 1 (1A) of the periodic table. In their elemental form, the alkali metals have a shiny, metallic appearance, but they are also very soft and can be easily cut by hand. Due to their high reactivity, however, the alkali metals do not exist in their elemental form in nature.Because the alkali metals possess only a single valence electron with a low first ionization energy, the alkali metals (M) readily react with nonmetals and lose this electron to form cations with a +1 charge (M⁺) that are incorporated into ionic compounds. Consequently, elemental samples of alkali metals will rapidly tarnish in oxygen by forming oxides (Reaction 1) and vigorously react with elemental halogens (X₂) to form halide salts (Reaction 2) .2 M(s) + O₂(g) → M₂O(s) Reaction 12 M(s) + X₂(g) → 2 MX(s) Reaction 2Alkali metals also react violently with water to form very basic metal hydroxide (alkali) solutions while releasing hydrogen gas in the process (Reaction 3) .2 M(s) + 2 H₂O(l) → 2 MOH(aq) + H₂(g) Reaction 3As demonstrated by these reactions, alkali metals possess a low electron affinity that makes accepting an additional electron to form an anion less favorable than losing the valence electron to form a cation.Of the alkali metals, francium is the rarest since it is a trace radioactive byproduct formed from the decay of uranium ores and has a very short half-life. As a result, any francium formed will quickly decay into radium or astatine by beta decay or by alpha decay, respectively.Whereas hydrogen is a part of Group 1 based on its number of valence electrons, hydrogen is not an alkali metal. Interestingly, some research has suggested that under extreme pressures and very low temperatures, hydrogen may form a solid with metallic properties.
-Which of the following alkali metals is LEAST likely to accept an additional electron?

Question

Quizplus · Accepted Answer

11ecba2d_11e0_4e86_a3bf_e70ba5870ccc_MD0008_00 Electron affinity is defined as the change in energy resulting from adding an electron (e⁻) to a neutral atom of an element (X) in the gas state to form an anion with a −1 charge: X + e⁻ → X⁻ When a stable anion is formed, energy is released as a product and a negative value results for the change in energy (energy of the products minus energy of the reactants) from the process. Therefore, electron affinity values with a more negative magnitude indicate elements that more readily accept the addition of an electron. In general, an additional electron is often more easily accepted by nonmetals than by metals. Periodic trends show that apart from some intermittent, regional exceptions caused by atomic size and orbital-filling effects, electron affinity tends to become stronger (more negative) moving left to right across a period and tends to become weaker (less negative) moving down a group on the periodic table. Consistent with these general trends, the electron affinity of the alkali metals in Group 1 weakens moving down the column. Therefore, cesium (Cs) has the weakest electron affinity and is the least likely (least favorable) to accept an additional electron. (Choices A, B, and C) Sodium (Na), potassium (K), and rubidium (Rb) are all alkali metals, but each has a stronger electron affinity than cesium (Cs). Adding an additional electron to Na, K, or Rb forms a more stable anion and releases more energy than is released from Cs. Educational objective: Electron affinity is the change in energy associated with adding an electron to a neutral atom in the gas state. Values with a more negative magnitude indicate elements that more readily accept the addition of an electron. With some intermittent exceptions, electron affinity tends to become stronger (more negative) moving left to right across a period and tends to become weaker (less negative) moving down a group on the periodic table.