Chapter 11: Group 2

A major physical trend is the **increase in atomic size, or metallic radius, corresponding decrease in the first and second ionization energies. Because it becomes progressively easier to remove these two valence electrons, the chemical reactivity of the Group 2 metals increases as the group is descended. The elements act as reducing agents, readily forming stable divalent ions. When reacting with dilute acids like hydrochloric acid, the metals yield hydrogen gas and a soluble chloride salt, a reaction that is visibly more vigorous for elements lower in the group. However, the metals' reaction with dilute sulfuric acid often halts for calcium, strontium, and barium because the resulting sulfates exhibit a decreasing solubility trend going down the group, leading to a protective, insoluble surface layer being formed. The metals also react with oxygen to form white, basic metal oxides. Furthermore, the oxides and hydroxides react with water, and the alkalinity of the resulting solutions increases down the group because the solubility of the Group 2 hydroxides increases significantly from magnesium to barium. The thermal stability of the Group 2 carbonates and nitrates follows an inverse trend, requiring a higher temperature for decomposition as one descends the group. Finally, the chapter notes that calcium, strontium, and barium compounds can be identified using flame tests, which produce characteristic colors such as brick-red, scarlet/red, and apple-green, respectively.