13.1: Properties of Group 1 Metals This page discusses the trends in some atomic and physical properties of the Group 1 elements - lithium, sodium, potassium, rubidium and cesium. Sections below cover the trends in atomic radius, first ionization energy, electronegativity, melting and boiling points, and density. Group 1 Trends 13.2: Reactivity of Group 1 Metals Alkali metals are among the most reactive metals. This is due in part to their larger atomic radii and low ionization energies. They tend to donate their electrons in reactions and have an oxidation state of +1. These metals are characterized by their soft texture and silvery color. They also have low boiling and melting points and are less dense than most elements. All these characteristics can be attributed to these elements' large atomic radii and weak metallic bonding. Flame Tests Group 1 Compounds Reactions of Group 1 Elements with Chlorine Reactions of Group 1 Elements with Oxygen Reactions of Group 1 Elements with Water 13.3: Chemistry of Lithium (Z=3) Chlorine is a halogen in Lithium is a rare element found primarily in molten rock and saltwater in very small amounts. It is understood to be non-vital in human biological processes, although it is used in many drug treatments due to its positive effects on the human brain. Because of its reactive properties, humans have utilized lithium in batteries, nuclear fusion reactions, and thermonuclear weapons. 13.4: Chemistry of Sodium (Z=11) Sodium is metallic element found in the first group of the periodic table. As the sixth most abundant element in the Earth's crust, sodium compounds are commonly found dissolved in the oceans, in minerals, and even in our bodies. 13.5: Chemistry of Potassium (Z=19) In its pure form, potassium has a white-sliver color but it quickly oxidizes upon exposure to air, tarnishing in minutes if it is not stored under oil or grease. Potassium is essential to several aspects of plant, animal, and human life and is thus mined, manufactured, and consumed in huge quantities around the world. 13.6: Chemistry of Rubidium (Z=37) Rubidium (Latin: rubidius = red) is similar in physical and chemical characteristics to potassium, but much more reactive. It is the seventeenth most abundant element and was discovered by its red spectral emission in 1861 by Bunsen and Kirchhoff. Its melting point is so low you could melt it in your hand if you had a fever (39°C). But that would not be a good idea because it would react violently with the moisture in your skin. 13.7: Chemistry of Cesium (Z=55) Cesium is so reactive that it will even explode on contact with ice! It has been used as a "getter" in the manufacture of vacuum tubes (i.e., it helps remove trace quantities of remaining gases). An isotope of cesium is used in the atomic clocks. 13.8: Chemistry of Francium (Z=87) Francium is the last of the known alkali metals and does not occur to any significant extent in nature. All known isotopes are radioactive and have short half-lives (22 minutes is the longest).