Metals and Non-Metals
Metals– Metals occur in nature in the free state as well as in the combined state, as very few metals occur in the free state like – Gold, Silver, and Platinum.
- Metals found in combined states in a mineral and Ore
- Mineral- The element and compounds which are found naturally in the earth’s crust.
- Ore- these contain a high percentage (quantity) of a particular metal that can be extracted on large scale.
- These may be classified as – Alkaline earth metals, alkali metals, transition metals, actinides, and lanthanides, on the basis of their position in periodic table.
Properties of Metals
Physical properties of metals
- Most metals found in solid states. Exception-Mercury (the metal is liquid at room temperature. Alkalis metals like lithium, sodium, potassium are so soft and can be cut with a knife.)
- consisting of a High melting point and high boiling point. (Gallium and Caesium Having extremely low Melting point as they can melt even on palm)
- They are ductile. (Ductile- Ability of metals to be drawn into thin wires.) For ex- Gold is the most ductile metal.
- malleable (they can be beaten into thin sheets.)- Gold and silver are the most malleable metals.
- Quite lustrous property (metallic luster)
- Good conductor of heat and electricity. Silver (best conductor) and copper are the best conductors of heat and electricity.
- Bad conductor of heat and electricity: Lead is the worst conductor and Iron and mercury are poor conductors of heat.
Chemical properties of metals
- These are electropositive and form positive ions by losing electrons.
- They form metal oxides by combining Oxygen.
for example, if copper is heated in air it forms copper (II) oxide by combining oxygen.
- Most metal oxides are insoluble in water but few dissolve in water and form Alkalis. For example, Sodium oxide and Potassium oxide dissolves in water and produces alkalis as-
- Different metals having different reactivity rates with oxygen. Some metals like Potassium and sodium react vigorously with oxygen so they catch fire if kept in open, for protecting accidental fire such metals always kept in kerosene oil.
- Silver and gold are not reactive to oxygen even at high temperatures.
- The process of forming a thick oxide layer of aluminum is called Anodising.
- They form Halides with Halogens.
- The reactivity of metals varies and the alkali metals i.e. first groups of elements are most reactive.
- Metals react with water to form metal oxides and hydrogen gas. (All metals do not react with water)
- Magnesium reacts with hot water (not cold water), and it forms magnesium hydroxide and hydrogen and it starts floating because the bubbles of hydrogen gas get stick on its surface.
- Metals like Aluminium, iron, and zinc only react with steam (neither hot nor cold water) to form a metal oxide and hydrogen.
- Reaction with Acids– Some metals react with acid to give Salt and Hydrogen gas, but all reactions do not result in the same manner. For example, when a metal reacts with Nitric acid, Hydrogen gas does not evolve because HNO3 is a strong oxidizing agent. The reactivity of metals decreases in order– Mg>Al>Zn>Fe. Copper does not react with Dilute HCL.
- Most reactive Metals- Ex. Potassium (K), Sodium (Na)
- Least Reactive-Ex. Silver (Ag), and Gold (Au)
These may be either solids or gases. Bromine is an exception found in Liquid form. Examples of non-metals are Carbon, Sulphur, Iodine, Oxygen, Hydrogen, etc.
- Mostly these are not lustrous, Iodine is lustrous non-metal.
- They do not conduct heat and electricity. (graphite- allotrope of carbon, is the conductor of electricity)
- Mostly their melting point less than metals. (Diamond, an allotrope of carbon is the hardest natural substance, having very high melting and boiling point)
- Neither malleable nor ductile.
- They form hydrides reacting with hydrogen.
Metals and Non-metals react as a tendency to attain a completely filled valence shell.
These are characterized as a neutral compound that is made up of positive and negative charges called cation and anion respectively. These compounds generally named as the first the name of the cation followed by anion. The compound’s ions held together by an electrostatic force called ionic bonding.
An example of an Ionic bond is as simple – sodium chloride (NaCl) i.e. made with Na+ and Cl- Ion.
Properties of ionic compounds–
- Ionic compounds are solid and hard as they have a strong force of attraction between positive and negative ions. These are mostly brittle and break into pieces when pressure is applied.
- Having high melting and boiling point, ex- NaCl- having melting point 1074 and boiling point- 1686.
- generally soluble in water.
- ionic compound conducts electricity in a molten state.
The occurrence of Metals
The earth’s crust is a major source of metals. The elements or compounds found naturally in the earth’s crust are called minerals. The minerals which are containing a higher percentage of particular metals and the metal extracted from them is called ore.
The occurrence of some Metals:
The process of Extraction of metals from their ores is termed a metallurgical process. There are many metallurgical operations such as-
- Smelting– Process of heating of ore above melting point by this whole mixture reduce the ore to metal. It is a chemical-changing process.
- Flux– flux is the substance added to ore during the process of smelting for removing gangue (impurities).
- Slag– The waste material formed by the chemical combination of gangue and flux during the extraction of metal is called Slag.
- Calcination– Volatile impurities of most ores are removed by strong heating, the process is called calcination.
- Roasting– In this process Ore is heated below its melting point at a constant temperature in a controlled air supply is called roasting. For example- impurities like sulfur, arsenic, etc oxidized and converts into volatile oxides, and by this only metallic oxides remain.
- The concentration of ore– By this process gangue is separated from the ore. The processes of concentration of ores are:
- Gravity separation- ores of higher density
- Oil floatation- sulfide ores
- Process of magnetic concentration- impurities of ore
- leaching process.
- Refining of metals– Extraction of pure metal from impure metals produced by various processes. In refining, the widely used process is Electrolytic refining. Electrolytic refining is used for Zinc, nickel, silver, gold, etc.
Example of some important elements and their utilities