Of the 118 elements known to man, 94 are metals. These are elements that form simple substances with a characteristic sheen, high ductility and ductility. What other properties do metals have? What groups are they divided into? Let's find out.
Metals and their properties
Description of metals is not an easy task. They are difficult to compare with other elements or substances known in the modern world. In the standard sense, metal is a solid gray substance with a strong sheen. But everything is much more complicated. Most of them are really gray, but the shades are different for everyone. In gallium it is bluish, in bismuth it is pink, in copper it is bright red, but cesium, strontium and gold have a yellow tint.
By the degree of manifestation of their properties, metals are very different. But there are qualities that unite them. Metals relatively easily give electrons to the external level, since they are weakly bound to the nucleus of an atom. Their internal structure is represented by a crystal lattice; therefore, under normal conditions, they are all solid. The only exception is mercury, which hardens only at temperatures below -38.83 ° C.
Metals are excellent conductors of heat and electricity. Many of them are very plastic, for example gold, copper, pure chrome, silver. They are able to bend or crumple without breaking. Others are quite fragile (manganese, tin, bismuth).
Metal groups
Under the same conditions, metals behave differently, as is already seen with mercury. It very easily becomes liquid, but not all substances behave the same. Depending on the melting temperature, fusible and refractory metals are distinguished. The latter include tungsten, tantalum, rhenium, molybdenum. They melt at temperatures above 2000 ° C.
Heavy and light metals are also emitted. Severe - lead, cadmium, cobalt, mercury, copper, vanadium, have a large atomic weight (more than 50) and high density. In the lungs, everything is exactly the opposite. These include aluminum, gallium, indium. The lightest is lithium, with a density of 0.533 g / cm³ and an atomic mass of 3.
The alkaline group of metals (lithium, sodium, potassium, rubidium) is also isolated in the periodic table. They quite readily react with water, forming a soluble alkali or hydroxide. All of them are very active, soft and much lighter than water. Alkaline earth metals also exist (calcium, barium, strontium), their oxides or earths form alkali with water. They are harder and not as active as alkaline.
Based on the different properties of metals, they are also divided into:
- Transitional.
- Post-transition.
- Colored.
- Black.
- Lanthanides
- Actinoids.
- Noble.
- Platinum group metals.
- Rare earths.
Noble metals
Metals in chemical reactions often act as reducing agents. Giving away their electrons, they undergo corrosion processes that destroy them. Under the action of oxidizing agents, oxides and hydroxides are formed on their surface, which are popularly called rust.
Many metals are subject to such processes. Destroyers for them can be gases and various liquids. However, there is a separate class of metals that are practically not susceptible to oxidation and rust. These are noble metals. All of them are also rare and precious. Their cost ranges from 300 (silver) dollars to 70,000 (rhodium) dollars per kilogram.
Noble are gold, silver, as well as metals of the platinum group: platinum, ruthenium, osmium, palladium, iridium, rhodium. Platinum, palladium, gold and silver are very plastic, but they cannot withstand too high temperatures. Other precious metals are also refractory; they melt from a temperature of 2334 ° C (ruthenium) to 3033 ° C (osmium).
All of them withstand the effects of water and air, but can react with more aggressive substances. For example, silver easily dissolves in nitric acid, and darkens when it comes in contact with iodine. By the way, with the help of iodine you can check whether the product is really silver.
Being in nature
Metals are widely distributed on our planet. In the form of salts and compounds, they are found in sea water. Most of all, it is full of magnesium (0.12%) and calcium (1.05%). In the earth's crust, the most common metal is aluminum. It makes up about 8% of its total mass. It also contains a lot of iron (4.1%), calcium (4%), sodium (2.3%), magnesium (2.3%), potassium (2.1%).
But metals are present not only in the external environment. They are present in any living organism, responsible for many vital functions. The human body contains about 3% of metals. Iron in the blood helps hemoglobins to attach oxygen and exchange with carbon dioxide. Magnesium is in the muscles and nervous system. He is involved in the synthesis of proteins, is responsible for muscle relaxation, inhibits the excitation of nerve endings.
The most necessary for us: magnesium, iron, sodium, calcium, potassium, zinc, copper, cobalt, manganese and molybdenum. Metals are found in bones, in the brain, in the tissues of other organs. We get them with water and food, and we constantly need to replenish their supplies. With a deficiency of these elements, the body does not work correctly, however, their excess is also not good.
Application
People have learned to use metals in almost all areas of their lives. They make structural materials, wires, electrical equipment, utensils. Unstable radioactive elements, such as uranium, California, polonium, have found application in nuclear energy and weapons production.
Light and durable metals are used in space technology and the automotive industry. Various elements are used in pharmaceuticals, food, textile industry. They make jewelry, household items, as well as medicines and medical instruments. Lithium, for example, is used as an antidepressant; gold is a remedy for arthritis and tuberculosis. Titanium and tantalum are used in surgery for prostheses and replacement of damaged parts of the body.