Metals and Non-metals

Metals are elements that are typically hard, shiny, malleable, ductile, and good conductors of heat and electricity. Non-metals lack these properties, being brittle, poor conductors, and not shiny. For example, iron is a metal, while sulfur is a non-metal.

Metals have lustrous surfaces, are malleable (can be hammered into sheets), ductile (can be drawn into wires), and conduct heat and electricity well. They are generally solid at room temperature, except mercury, which is liquid.

The reactivity series lists metals in order of their decreasing reactivity. Potassium is the most reactive, and gold is the least. This series helps predict displacement reactions and the extraction of metals from their ores.

Metals react with oxygen to form metal oxides, which are usually basic. For example, magnesium burns in air to form magnesium oxide. Some metal oxides, like aluminum oxide, are amphoteric, reacting with both acids and bases.

Metals react with water to form metal hydroxides and hydrogen gas. Highly reactive metals like sodium react violently, while less reactive metals like iron react slowly or need steam. For example, sodium reacts with water to form sodium hydroxide and hydrogen.

Metals react with dilute acids to form salts and hydrogen gas. The reactivity determines the reaction's vigor. For example, zinc reacts with hydrochloric acid to form zinc chloride and hydrogen.

Roasting involves heating sulfide ores in excess air to convert them into oxides, releasing sulfur dioxide. Calcination heats carbonate ores in limited air to form oxides, releasing carbon dioxide. Both processes are steps in metal extraction.

Gold is unreactive and does not easily combine with other elements, so it is found as nuggets or grains in nature. Its low reactivity places it at the bottom of the reactivity series.

An alloy is a homogeneous mixture of two or more metals, or a metal with a non-metal, to enhance properties. For example, brass is an alloy of copper and zinc, used for making musical instruments.

Corrosion is prevented by methods like painting, oiling, galvanizing, and alloying. Galvanizing coats iron with zinc to protect it from rusting, even if the coating is broken.

The thermit reaction is a highly exothermic displacement reaction where aluminum reduces iron oxide to molten iron, used for welding railway tracks. The equation is Fe2O3 + 2Al → 2Fe + Al2O3 + heat.

Sodium and potassium are highly reactive with air and water, catching fire when exposed. Storing them under oil prevents contact with moisture and oxygen, ensuring safety.

Amphoteric oxides react with both acids and bases to form salts and water. Examples include aluminum oxide and zinc oxide, which react with hydrochloric acid and sodium hydroxide.

Aluminum is extracted from bauxite ore by electrolysis. The process involves dissolving alumina in cryolite to lower its melting point, then passing electricity to decompose it into aluminum and oxygen.

The reactivity series helps predict metal reactions, displacement reactions, and extraction methods. Metals above carbon in the series are extracted by electrolysis, while those below are reduced by carbon.

Ionic compounds have high melting points due to strong electrostatic forces between oppositely charged ions. A lot of energy is required to break these bonds, as seen in sodium chloride.

Electrolytic refining purifies metals by making the impure metal the anode and a pure metal strip the cathode in a metal salt solution. On passing current, pure metal deposits on the cathode, leaving impurities as anode mud.

Copper is used for electrical wiring because it is highly ductile and an excellent conductor of electricity. Its alloys, like brass, are not as conductive, making pure copper ideal for this purpose.

Non-metals are used in various applications, like oxygen for respiration, nitrogen in fertilizers, and chlorine for water purification. Carbon, in the form of graphite, is used in pencils and as a lubricant.

Rust forms when iron reacts with oxygen and water to form hydrated iron(III) oxide. The reaction is accelerated by salt and acids, leading to the reddish-brown flaky coating seen on iron objects.

Metals tend to lose electrons to form positive ions, while non-metals gain electrons to form negative ions. This difference is due to their positions in the periodic table and their electronegativities.

Stainless steel is resistant to rust because it is an alloy of iron with chromium and nickel. Chromium forms a passive oxide layer that prevents further corrosion, making it ideal for cutlery and surgical instruments.

Graphite is used in pencils because it is a non-metal that is soft and leaves marks on paper. Its layered structure allows sheets to slide off easily, making it suitable for writing and drawing.

Metals are malleable and ductile, so they flatten or bend when struck with a hammer without breaking. Non-metals are brittle and shatter or crumble under the same conditions, like sulfur or phosphorus.

Metallurgy is crucial for extracting metals from ores and refining them for use. It enables the production of pure metals and alloys with desired properties, essential for construction, electronics, and transportation.