All known matter is made up of atoms, from the 112 chemical elements that make up the periodic table. These elements are classified, according to their nature and properties, into metals and nonmetals.
Differences between metals and nonmetals
Metals and nonmetals are distinguished in their fundamental properties and their types of possible reactions.
- The metals are, with the exception of mercury, solid at room temperature. They are glossy, more or less ductile and malleable, and are good conductors of electricity and heat. In contact with oxygen or acids, they oxidize and corrode (loss of electrons) since their outer layers have a low incidence of electrons (3 or less).
- The nonmetals, however, are typically poor conductors of electricity and heat, very varied appearances, and melting points usually well below metals. Many exist only in the diatomic (molecular) formula, can be soft like sulfur or hard like diamond, and can be found in any of the three states of matter: gaseous, liquid, and solid. Furthermore, their appearance does not usually reflect light and they can have different colors.
Finally, metallic elements tend to be united by electromagnetic relationships (charged ions), while non-metallic elements form complex molecular structures through bonds of various kinds (hydrogen, peptides, etc.). Hence, organic or life chemistry is that of the latter, although living bodies are made up of combinations of both types of elements.
Examples of metals
- Iron (Fe). Also called iron, it is one of the most abundant metals in the earth’s crust, which makes up the very heart of the planet, where it is in a liquid state. Its most striking property, apart from its hardness and fragility, is its great ferromagnetic capacity. Through alloying it with carbon it is possible to obtain the steel.
- Magnesium (Mg). The third most abundant element on earth, both in its crust and dissolved in the seas, never occurs in nature in its pure state, but as ions in salts. It is essential for life, usable for alloys, and highly flammable.
- Gold (Au). A shiny, soft, yellow-colored precious metal that does not react with most chemicals except cyanide, mercury, chlorine, and lye. Throughout history, it played a vital role in human economic culture, as a symbol of wealth and endorsement of coins.
- Silver (Ag). Another precious metal, it is white, shiny, ductile and malleable, it is found in nature as part of various minerals or as pure sheets of the element since it is very common in the Earth’s crust. It is the best-known conductor of heat and electricity.
- Aluminum (Al). Very light, non-ferromagnetic metal, the third most abundant in the Earth’s crust. It is highly valued in industrial and steel trades since higher strength variants can be obtained through alloys, but that retain their versatility. It has a low density and very good resistance to corrosion.
- Nickel (Ni). Very ductile and very malleable white metal, a good conductor of electricity and heat, as well as being ferromagnetic. It is one of the dense metals, along with iridium, osmium, and iron. It is vital for life, as it is part of numerous enzymes and proteins.
- Zinc (Zn). It is a transition metal similar to cadmium and magnesium, often used in galvanizing processes, that is, a protective coating for other metals. It is very resistant to cold plastic deformation, so it works above 100 ° C.
- Lead (Pb). The only element capable of stopping radioactivity is lead. It is a very particular element, given its unique molecular flexibility, ease of melting, and relative resistance to strong acids such as sulfuric or hydrochloric.
- Tin (Sn). Heavy and easily oxidized metal, used in many alloys to provide resistance to corrosion. When folded, it produces a very characteristic sound that has been dubbed the “tin cry.”
- Sodium (Na). Sodium is a soft, silver alkali metal present in sea salt and in the mineral called halite. It is highly reactive, oxidizable, and has a violent exothermic reaction when mixed with water. It is one of the vital components of known living organisms.
Examples of non-metals
- Hydrogen (H). The most common and abundant element in the universe is a gas that is found both in the atmosphere (as a diatomic molecule H 2 ) and as part of the vast majority of organic compounds, and also burning by fusion in the hearts of the stars. It is also the lightest, most odorless, colorless, and water-insoluble element.
- Oxygen (O). Indispensable for life and used by animals for their energy (respiration) processes, this highly reactive gas (O 2 ) forms oxides with almost all the elements on the periodic table except noble gases. It forms almost half of the mass of the earth’s crust and is vital for the appearance of water (H 2 O).
- Carbon (C). The central element of all organic chemistry, common to all known living things and part of more than 16 million compounds that require it. It is found in nature in three different forms: carbon, graphite, and diamonds, which have the same number of atoms but arranged in different ways. Together with oxygen, it forms carbon dioxide (CO 2 ) essential for photosynthesis.
- Sulfur (S). A soft, abundant element with a characteristic odor, it is common to the activity of almost all living organisms, and abundant in volcanic contexts. Yellowish and insoluble in water, it is essential for organic life and extremely useful in industrial processes.
- Phosphorus (P). Despite never being in a native state in nature, it is an indispensable part of many organic compounds and living things, such as DNA and RNA, or ATP. It is very reactive and emits light upon contact with oxygen.
- Nitrogen (N). Normally diatomic gas (N 2 ) constitutes 78% of the air in the atmosphere and is present in many organic substances such as ammonia (NH 3 ), despite being gas of low reactivity compared to hydrogen or oxygen.
- Helium (He). The second most frequent element in the universe, especially as a product of the stellar fusion of hydrogen, from which heavier elements emerge. It is a noble gas, that is to say, of almost no reactivity, colorless, odorless and very light, often used as an insulator or as a refrigerant, in its liquid form.
- Chlorine (Cl). Chlorine in its purest form is a highly toxic yellowish gas (Cl) with an unpleasant odor. However, it is abundant in nature and is part of numerous organic and inorganic substances, many of which are essential for life. Along with hydrogen, it forms hydrochloric acid (HCl), one of the most powerful that exists.
- Iodine (I). The element of the group of halogens, is a little reactive and electronegative, despite which it is used in medicine, in the photographic arts, and as a dye. Despite being a non-metal, it has curious metallic characteristics and is reactive to mercury and sulfur.
- Selenium (Se). Insoluble in water and in alcohol, but soluble in ether and carbon disulfide, this element has photoelectric properties (it converts light into electricity) and is a necessary part of glass manufacturing. It is also a nutrient for all life forms, essential for many amino acids, and present in many foods.