The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:
Metals are the elements that ionise by losing electrons. They form positive ions by losing the electrons. Non-metals accept electrons and form negative ions. Sodium, potassium, and aluminium are some examples of metals, and carbon, sulphur, and nitrogen are a few non-metals.
Below are the distinguishing points between metals and non-metals
MetalsNon-MetalsThese are solid at room temperature and have lustre.These are either gases or soft solids and do not possess lustre.They are good conductors of electricity except for Tungsten.They are bad conductors of electricity except for carbon and graphite.They have high melting and boiling points and have high density.They have low melting and boiling points and are less dense.They have valence electrons 1, 2, or 3.They have valence electrons 4 to 7.They lose electrons and are reducing agents.They gain electrons and are oxidising agents.They release hydrogen when diluting with acids.They do not release hydrogen when diluting with acids.
Metals exist in nature in impure form. The crust of the earth is the main source of metal. Metals exist both in combined form or in the free state. Gold and mercury are available in the free state. Sodium and magnesium are present as chlorides. The metals present in a combined state are called minerals.
Metals are present inside the earth in impure form. They need to be extracted and transformed into pure form. Metallurgy is the process of extraction of metals from the ore in pure form. The metals, when extracted from ore, have soil, sand, rock, and limestone combined. These limestone, rock, and salt are called ores. The impurities that get removed during the process of metallurgy are called flux.
Metallurgy follows the below steps:
Step1: Concentration of Ore
In this step, the matrix gets separated from the ore. This step uses the below principles of extraction.
Step2: Ore conversion to metal oxide
In this step, the concentrated ore gets converted into metal oxides using one of the below methods:
Step3: Reduction of metallic oxides to metal
In this step, the metal oxide gets reduced to metals. It is done using the process of electrolysis or with the help of reducing the agents.
In this step, the impure metal gets refined to get pure metal. Below methods are used for refining:
Aluminium ore, also called bauxite, follows the metallurgy process for the extraction of aluminium. Below steps are followed to extract aluminium from bauxite.
Step1: Baeyer’s process
This is the step of concentration of aluminium ore called bauxite. It is the chemical method in which aluminium oxide is treated with sodium hydroxide. As a result, sodium aluminate is formed, which is soluble and can be filtered. The filtrate then gets heated with water that forms aluminium hydroxide crystals. Aluminium hydroxide is heated strongly to form alumina.
Step2: Hall Heroult’s Process
Hall Heroult’s process is the method of extraction of aluminium. It is the process of electrolytic extraction in which Na3AlF6 or CaF2 gets mixed with alumina (Al2O3). It helps in reducing the melting point and makes it conduct electricity. This process is followed in the steel vessel having carbon lining and graphite rods immersed in the vessel. The carbon lining of the vessel acts as a cathode, and the graphite rods act as an anode. When electricity is passed, oxygen forms at the anode. Oxygen released at anode combines with carbon to form carbon dioxide and carbon monoxide. Aluminium ions get accumulated at the cathode and then settle at the bottom.
The aluminium collected by Hall Heroult’s process is almost 99.5% pure.
To conclude, metals are the elements that ionise to form positive ions. The occurrence of metals in nature is a free or combined state. The metals present in the combined state have to go through the process of metallurgy to get extracted as refined in pure form.