The elements have one form of classification where they are broadly classified as metals, non-metals and metalloids. Metals and non-metals are generally heard of but here we will also study about the intermediate type of elements called metalloids. This type of classification is based on the shared physical and chemical properties. A jagged black line in a periodic table (see figure below) along the right side of the table separates the metals from the nonmetals. To the right of the line lie nonmetals, the metals are to the left of the line(except hydrogen, which is a nonmetal), and the elements which lie immediately adjacent to the line are the metalloids.
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A metal is generally a hard solid substance that has a shiny lustre and it conducts heat and electricity. Metals are good conductors of heat and electricity. Silver is the best conductor of heat. Metals also possess malleability that is they can be hammered into sheets. Metals being ductile can be drawn into wire. At room temperature, most of the metals are solids and have a characteristic silvery shine (except for mercury, which is a liquid). The melting points of metals are usually high but gallium and caesium are those metals having such low melting points that they will melt if you keep them on your palm. Another exception to general characteristics of metals are alkali metals such as lithium, sodium, potassium which are so soft that they can be cut with a knife. Also, they have low densities and low melting points. Lead, mercury, titanium, chromium are bad conductors of heat. Bismuth is the poorest conductor of heat.
A metal can be defined chemically as an element that readily forms positive ions (cations) and has metallic bonds. They tend to lose electrons easily. While the traditional definition focuses on the bulk properties of metals, they are sometimes also described as a lattice of positive ions surrounded by a cloud of delocalized electrons.
The reactivity series is a series of metals where the arrangement is done in the order of their decreasing activities.It is developed after performing displacement experiments.
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Nonmetals are those elements which generally lack the properties of metals or have their properties opposite to that of metals. Their thermal and electrical conductivities are usually poor. They are brittle and do not possess the properties of malleability and ductility. Elemental nonmetals mostly are in a gaseous state at room temperature, while others are solids. Bromine is a non-metal which is liquid. Non-metals lack the shiny lustre except iodine. Generally, nonmetals have low melting and boiling points. Carbon is a nonmetal that can exist in different forms called allotropes. Diamond is an allotrope of carbon and is the hardest natural substance known and has very high melting and boiling point. So it is an exception in the case of nonmetals. Also graphite, another allotrope of carbon is a good conductor of electricity which is another exception. Non-metals are less dense as compared to metals.
Non-metals are elements which form negative ions(anions) by accepting or gaining electrons. They generally have 4,5,6 or 7 electrons in their outermost shell so they tend to gain electrons during chemical reactions.
The metalloids are intermediate in their properties between metals and nonmetals. Taking physical properties into consideration, they are more like the nonmetals, but under certain circumstances, contrary to the expected behaviour many of them can be made to conduct electricity. These semiconductors find their use in computers and other electronic devices. They can have a dull or metallic appearance. In a periodic table, these elements run diagonally. They are usually brittle. They form alloys with metals. They can both gain or lose electrons in a chemical reaction. Due to their unique properties, they find their use as catalysts, biological agents, flame retardants, alloys and semiconductors in industries. Boron, silicon, germanium, arsenic, tellurium and antimony are some commonly known metalloids.
Metalloid, in chemistry, is a term which describes a chemical element forming a simple substance having properties intermediate between those of a typical metal and a typical nonmetal. They are often called semi-metals.
1. What is the Rarest Metal?
Rhodium is the rarest metal on earth. It is a silver-white metallic element that is highly reflective and resistant to corrosion. It is considered as the rarest and most precious metal in the world well above gold or silver. Rhodium is the rarest of the platinum group, only occurring up to one part per 200 million in the Earth's crust. It is unaffected by air and water up to 1,112 degrees Fahrenheit (600 degrees Celsius). The chemical symbol of rhodium is Rh. Its atomic number is 45 and has an atomic weight of 102.90550. It is solid at room temperature and has a density of 12.41g/cm³.
2. What are Some of the Uses of Non-Metals?
Iodine helps in throat infections and is used as an antiseptic in wounds and cuts.
Chlorine is used as a bleaching agent. It is added in drinking water to kill harmful bacteria.
Helium is used in scientific experiments as an inert gas. It is also used in balloons.
Apart from an important role in respiration process, oxygen also finds its use in the manufacturing of steel and metal fabrication.
Sulphur and Phosphorous are used in fireworks.
Nitrogen is used in fertilizers.
Charcoal, an amorphous form of carbon is used in ultrafiltration and to control bad odour in the refrigerator.