Predicting and identifying reactions and products Study Guide

Transition metals are a group of metallic elements found in the central block of the periodic table. Unlike Group 1 alkali metals, they generally possess high melting points, high densities, and are strong and hard. Many transition metals are good conductors of heat and electricity. A distinctive characteristic is their ability to form coloured compounds, which can be seen in various minerals and solutions. For example, copper compounds are often blue or green, while iron compounds can be green (iron(II)) or rust-brown (iron(III)). Transition metals can also have multiple oxidation states, meaning they can form ions with different charges. This property is linked to their use as catalysts, substances that speed up chemical reactions without being used up themselves. For instance, iron is used in the Haber process to make ammonia, and nickel can be used to catalyse the hydrogenation of alkenes to alkanes. Copper is widely used for electrical wiring due to its excellent conductivity and ductility, and for plumbing due to its corrosion resistance. Iron is a key component of steel, an alloy used extensively in construction and manufacturing. These properties make transition metals highly valuable in industry and everyday life.

The reactivity of a metal is directly linked to its tendency to form a positive ion. Metals react by losing electrons to form positive ions (cations). The more readily a metal loses its outer shell electrons, the more reactive it is. This is why highly reactive metals like potassium and sodium react vigorously with water and dilute acids, forming positive ions and releasing hydrogen gas. Less reactive metals, such as copper or silver, do not readily lose their electrons and therefore do not react with water or dilute acids under normal conditions, or react very slowly. In general, the higher a metal is in the reactivity series, the more easily it loses electrons to form positive ions, and the more vigorous its reaction with water or dilute acids will be. For example, sodium is above magnesium in the reactivity series, so sodium loses electrons more easily and reacts more vigorously with water than magnesium does. When a metal reacts with water, it forms a metal hydroxide and hydrogen gas. When it reacts with a dilute acid, it forms a salt and hydrogen gas. In both cases, the metal atoms lose electrons to become positive ions, and hydrogen ions (from water or acid) gain electrons to become hydrogen gas (H2).