Metals: Properties, Uses, and Occurrence - PDF

 Metals Not all that glitter are gold, at least they contain free electrons. How many different uses of metal can you spot?  Typical Properties of Metals What are the general properties of most metals? solid at room temperature...

 Metals Not all that glitter are gold, at least they contain free electrons. How many different uses of metal can you spot?  Typical Properties of Metals What are the general properties of most metals? solid at room temperature high melting point good conductors of electricity and heat malleable: they can be shaped ductile: they can be drawn into wires strong dense Why do metals have these particular properties?  What is the structure of metals? The atoms in a pure metal are in tightly-packed layers, which form a regular lattice structure. The outer electrons of the metal atoms separate from the atoms and create a ‘sea of electrons’. These electrons are delocalized and so are free to move through the whole structure. The metal atoms become positively charged ions and are attracted to the sea of electrons. This attraction is called metallic bonding.  Why do metals have high melting points? Metals often have high melting points and boiling points. They have very high melting and boiling points because metallic bonding is very strong, so the atoms are reluctant to break apart into a liquid or gas. This property is due to the strong attraction between the positively-charged metal ions and the sea of electrons.  How Do Metals Conduct Heat And Electricity? Delocalized electrons in metallic bonding allow metals to conduct heat and electricity. For example, when a metal is heated, the delocalized electrons gain kinetic energy. These electrons then move faster and so transfer the gained energy throughout the metal. This makes heat transfer in metals very efficient. Delocalized electrons also conduct electricity through metals in a similar way. heat  Why are metals strong? Metals are usually strong, not brittle. When a metal is hit, the layers of metal ions are able to slide over each other, and so the structure does not shatter. metal before it is hit metal after it is hit force force The metallic bonds do not break because the delocalized electrons are free to move throughout the structure. This also explains why metals are malleable (easy to shape) and ductile (can be drawn into wires).  PROPERTIES OF METAL Hardness refers to the ability of a metal to resist abrasion, penetration, cutting action, or permanent distortion. Malleability, metals can be hammered, rolled, or pressed into various shapes without cracking or breaking or other detrimental effects Ductility is the property of a metal that permits it to be permanently drawn, bent, or twisted into various shapes without breaking. Elasticity is that property that enables a metal to return to its original shape when the force that causes the change of shape is removed.  Toughness- metals withstand tearing or shearing and may be stretched or otherwise deformed without breaking Fusibility is defined as the ability of a metal to become liquid by the application of heat PROPERTIES Conductivity is the property that OF METAL enables a metal to carry heat or electricity. Luster. Metals are shiny when cut, scratched, or polished. Sonorous. Metals often make a ringing sound when hit Metallic Bonding t Identify which property/properties of metal is described. A. Hardness B. Malleability C. Ductility D. Elasticity E. Toughness F.Metals are used in making jewelry and decoration Fusibility G. Conductivity H. Luster B, C, H I. Sonorous Identify which property/properties of metal is described. A. Hardness B. Malleability C. Ductility D. Elasticity E. Toughness F.Electric wires in are made of aluminum and copper. Fusibility G. Conductivity H. Luster C, G I. Sonorous Identify which property/properties of metal is described. A. Hardness B. Malleability C. Ductility D. Elasticity E. Toughness F.Metal wires are used in musical instruments. Fusibility G. Conductivity H. Luster C, B, I I. Sonorous Identify which property/properties of metal is described. A. Hardness B. Malleability C. Ductility D. Elasticity E. Toughness F.Titanium Fusibilityand other metal alloys are use in making G.planes. They were able to withstand heat and Conductivity H.corrosion. Luster A, B,D, E I. Sonorous FIVE GROUPS OF METALS Noble Metals found as pure metals nonreactive don’t combine with other elements to form compounds. Do not corrode easily ideal for jewelry and coins. copper, palladium, silver, platinum, and gold.  Alkali Metals very reactive do not occur freely in nature low melting points soft enough to be cut with a knife can explode if exposed to water malleable, ductile, good conductors of heat and electricity Alkali Earth Metals do not occur freely in nature less reactive than alkali metals, as well as harder, and have higher melting points  Transition Metals hard and shiny, strong, and easy to shape used for many industrial purposes form colorful compounds less reactive than the metals in Groups 1 and 2.  Poor Metals The poor metals are located in the p-block, and are the most electronegative but least reactive of all the metals. They are softer than the transition metals. melting and boiling points are generally lower than normal metals  The ease and speed with which an element combines, or reacts, with other elements and compounds is called its reactivity. Metals usually react by losing electrons to other atoms. Some metals are very reactive. Other metals don’t react at all with other metals. This means they can be found in a pure form (examples are gold Chemical Properties and platinum).  CHEMICAL PROPERTIES OF METALS 1. Metals when burned in the presence of oxygen, they combine with oxygen to form metallic oxides which are basic in nature. The general equation for this reaction is: metal + oxygen → metal oxide 2Mg + O2 ---> 2MgO MgO + H2O ---> Mg(OH)2  CHEMICAL PROPERTIES OF METALS 2. Different metals react differently with water. Sodium reacts violently with water forming sodium hydroxide and hydrogen. Magnesium reacts mildly with water but vigorously with steam. Zinc and iron react mildly with steam. Copper, gold and silver do not react with water at all. Most metals, on reacting with water produce hydroxide. 2Na + H2O 🡪 2NaOH + H2 CHEMICAL PROPERTIES OF METALS 3. Metals differ in their reactivity with acids. Most metals react with acids to produce salts and hydrogen. Metal + acid 🡪 Salt + Hydrogen Mg + 2HCl 🡪 MgCl2 + H2  CHEMICAL PROPERTIES OF METALS 4. Metals replace other metals. When an iron nail is placed in a test tube containing copper sulfate. The nail is coated with a layer of copper while the blue copper sulfate solution has turned greenish. The green solution is a solution of iron sulfate. Fe + CuSO4 ---> Cu + FeSO4 CHEMICAL PROPERTIES OF METALS 5. Most metals corrode when they are exposed to atmosphere.  What is Corrosion? Corrosion is the gradual destruction of a metal due to reactions with other chemicals in its environment. Over time, corrosion changes the appearance of the metal as it breaks down and becomes weaker. Corrosion can seriously damage metallic objects and structures. Coating the surface of a metal with paint and certain chemicals can protect it from corrosion.  Do All Metals Corrode? Metals behave differently when exposed to potassium the environment. sodium calcium A metal’s resistance to corrosion is related to magnesium its position in the reactivity series. The more aluminium increasing reactivity reactive a metal, the less resistant it is to zinc iron corrosion. lead Gold is an unreactive metal and does not copper corrode easily. Items made from gold can silver gold survive for thousands of years and have even platinum been found in good condition underwater.  What is Rusting? Rusting is the specific name given to the corrosion of iron. It is a chemical reaction between iron, oxygen and water. The chemical name for rust is hydrated iron (III) oxide. Acid rain and salt can increase the rate of rusting.  Why doesn’t aluminium corrode? Aluminium is a very reactive metal. However, it does not corrode in the presence of oxygen. Why is this? oxygen in the atmosphere coating of oxygen atoms aluminium atoms The outer aluminium atoms react with oxygen in the atmosphere to form a thin layer of aluminium oxide on the metal’s surface, which protects the metal from corrosion.  Occurrence of the Metals Most metals come from minerals. A mineral is a naturally occurring substance with a range of chemical composition. An ore is a mineral deposit concentrated enough to allow economical recovery of a desired metal. Metals exist in various forms In the Earth’s surface As ions in seawater In the ocean floor  METALLURGY the commercial extraction of metals from their ores and the preparation of metals for use. It usually includes several steps: 1. mining the ore 2. pretreatment of the ore 3. reduction of the ore to the free metal 4. refining or purifying the metal 5. alloying, if necessary.  Mining Five main types of mining: Open cast mining Underground mining Open pit mining Dredging Solution mining OPEN CAST MINING UNDERGROUND MINING OPEN PIT MINING Dredging Solution Mining  Also called ore dressing, the aim is to increase the amount of metal in each tonne of ore. The ore is crushed then ground and concentrated, the following Ore methods may be used: Concentration Gravity concentration Flotation Magnetic separation Amalgamation Gravity Concentration Some ores are heavier than the waste. The ore is shaken by a jolting box, or similar, while wet. Particles will separate into layers depending on weight, the metal may be removed as a layer. Flotation The fine particles of ore are swirled around in large tanks with air blown in and flotation agents added. The particles attach to the bubbles and float to the surface where the froth is skimmed off. Magnetic seperation In the seperation of ores that have magnetic properties, the ore is ground and passed over a rotating drum. The drum has a magnet inside it which holds the magnetic ore particles as the waste falls outside the screen. The ore held on the drum can be released or scraped off.  An alloy is a combination of metals or of a metal and another element. Alloys are defined by a metallic bonding character. An alloy may be a solid solution of metal elements (a single phase) or a mixture of Alloy metallic phases (two or more solutions).  Summary Main physical properties of metals are: lustrous, malleable, ductile, hard, dense, high boiling and melting points Metals are also good conductors because they have free electrons, have 1 to 3 electrons in the outermost shell of their atoms and tend to lose electrons and form cations Although many metals react with oxygen, water or even dilute acids, they react differently. Some metals are more reactive than others.  Summary Other metals are not easily attacked by or do not combine with air, water or chemicals. These metals are non-reactive, examples are gold and silver. Rusting is a special type of corrosion that takes place only in irons. Metals corrode but it is only irons that rust. Rusting could be prevented by methods that cover the surface of the metal. An alloy is a mixture of two or more different metals or a mixture of a metal and non-metal