What is an Element in Chemistry | Definition, Types

Definition of Element

In the light of this, an element may also be defined as a pure substance made of one kind of atom. Carbon, Sulphur, hydrogen, oxygen, nitrogen, iron, copper, gold, lead, etc., are familiar elements. An element is a pure substance consisting only of atoms with the same numbers of protons in their atomic nuclei.
elements in chemistry

Element is the simplest form of a pure substance that can neither be broken into nor built from simpler substances by ordinary physical and chemical methods.

Recent studies have revealed that the simplest form of matter is the atom.

The lightest chemical elements are hydrogen and helium. Both created by Big Bang nucleosynthesis during the first 20 minutes of the universe in a ratio of around 3:1 by mass (or 12:1 by a number of atoms), along with tiny traces of the next two elements, lithium, and beryllium.

Various natural methods made almost all other elements found in the nature of nucleosynthesis. On Earth, small amounts of new atoms are naturally produced in nucleogenic reactions or cosmogenic processes, such as cosmic ray spallation.

New atoms are also naturally produced on Earth as radiogenic daughter isotopes of ongoing radioactive decay processes such as alpha decay, beta decay, spontaneous fission, cluster decay, and other rarer decay modes.

Names of Elements

names of element

According to IUPAC, chemical elements are not proper nouns in English; consequently, the full name of an element is not routinely capitalized in English, even if derived from a proper noun, as in californium and einsteinium.

Isotope names of chemical elements are also uncapitalized if written out, e.g., carbon-12 or uranium-235. Chemical element symbols (such as Cf for californium and Es for einsteinium) are always capitalized.

In the second half of the twentieth century, physics laboratories became able to produce nuclei of chemical elements with half-lives too short for an appreciable amount of them to exist at any time.

These are also named by IUPAC, which generally adopts the name chosen by the discoverer. This practice can lead to the controversial question of which research group discovered an element.

This question delayed naming elements with an atomic number of 104 and higher for a considerable amount of time. (See element naming controversy).

Origin of the Elements

origin of elements

The fundamental reaction that produces the huge amounts of energy radiated by the Sun. And most other stars is the fusion of the lightest element, hydrogen, its nucleus having a single proton, into helium, the second lightest and second most abundant, with a nucleus consisting of two protons and two neutrons.

In many stars, helium production is followed by the fusion of helium into heavier elements, up to iron. The still heavier elements cannot be made in energy-releasing fusion reactions; an input of energy is required to produce them.

The proportion of different elements within a star—i.e., its chemical composition—is gradually changed by nuclear fusion reactions. This change is initially concentrated in the star’s central regions, where it cannot be directly observed.

Still, it alters some observable properties of the star, such as brightness and surface temperature. And these alterations are taken as evidence of what is going on in the interior.

Some stars become unstable and discharge some transmuted matter into interstellar space; this leads to a change in the chemical composition of the interstellar medium and of any stars subsequently formed.

The main problem concerned with the origin of the chemical elements is to decide to what extent the chemical composition of the stars seen today differs from the initial chemical composition of the universe and to determine where the change in chemical composition has been produced.

Periodic Table of Elements

periodic table of element

The periodic table of elements is widely used in the field of Chemistry to look up chemical elements as they are arranged in a manner that displays periodic trends in the chemical properties of the elements.

However, the Periodic table generally displays only the symbol of the element and not its entire name. Most of the symbols are similar to the element’s name, but some symbols of elements have Latin roots.

An example of this is silver which Ag denotes from its Latin name “Argentum”. Another such example would be the symbol ‘Fe’. Which denotes iron and can be traced to the Latin word for iron, “Ferrum.”

It could prove difficult for a beginner in chemistry to learn the names of all the elements in the periodic table. Because these symbols do not always correspond to the English names of the elements.

A list of the elements is available by name, atomic number, density, melting point, boiling point, symbol, and ionization energies of the elements.

The nuclides of stable and radioactive elements are also available as a list of nuclides, sorted by length of half-life for unstable ones.

One of the most convenient and certainly the most traditional presentation of the elements is in the form of the periodic table. Which groups together elements with similar chemical properties (and usually also similar electronic structures).

Abundance of Element

  • The abundance of elements in the Solar System is in keeping with their origin from nucleosynthesis in the Big Bang and a number of progenitor supernova stars. Very abundant hydrogen and helium are products of the Big Bang. Still, the next three elements are rare since they had little time to form in the Big Bang and are not made in stars (they are, however, produced in small quantities by the breakup of heavier elements in interstellar dust as a result of impact by cosmic rays). Beginning with carbon, elements are produced in stars by buildup from alpha particles (helium nuclei). Resulting in an alternatingly larger abundance of elements with even atomic numbers (these are also more stable). In general, such elements up to iron are made in large stars to become supernovas. Iron-56 is particularly common since it is the most stable element that can easily be made from alpha particles (being a product of the decay of radioactive nickel-56, ultimately made from 14 helium nuclei). Elements heavier than iron are made in energy-absorbing processes in large stars, and their abundance in the universe (and on Earth) generally decreases with their atomic number.
  • The abundance of the chemical elements on Earth varies from air to crust to ocean and in various types of life. The abundance of elements in Earth’s crust differs from that in the Solar System (as seen in the Sun and heavy planets like Jupiter) mainly in selective loss of the very lightest elements (hydrogen and helium) and also volatile neon, carbon (as hydrocarbons), nitrogen and sulfur, as a result of solar heating in the early formation of the solar system. Oxygen, the most abundant Earth element by mass, is retained on Earth by combination with silicon. Aluminum at 8% by mass is more common in the Earth’s crust than in the universe and solar system. Still, the composition of the far more bulky mantle, which has magnesium and iron in place of aluminum (which occurs there only at 2% of mass), more closely mirrors the elemental composition of the solar system, save for the noted loss of volatile elements to space, and loss of iron which has migrated to the Earth’s core.
  • The composition of the human body, by contrast, more closely follows the composition of seawater—save that the human body has additional stores of carbon and nitrogen necessary to form the proteins and nucleic acids, together with phosphorus in the nucleic acids. And energy transfer molecule adenosine triphosphate (ATP) that occurs in the cells of all living organisms. Certain organisms require particular additional elements, such as the magnesium in chlorophyll in green plants, the calcium in mollusk shells, or the iron in the hemoglobin in vertebrate animals’ red blood cells.
  • Of the 94 naturally occurring elements, those with atomic numbers 1 through 82 each have at least one stable isotope (except for technetium, element 43, and promethium, element 61, which have no stable isotopes). Isotopes considered stable are those for which no radioactive decay has yet been observed. Elements with atomic numbers 83 through 94 are unstable to the point that radioactive decay of all isotopes can be detected. Some of these elements, notably bismuth (atomic number 83), thorium (atomic number 90), and uranium (atomic number 92), have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced the heavy metals before the formation of our Solar System. At over 1.9×1019 years, over a billion times longer than the current estimated age of the universe, bismuth-209 (atomic number 83) has the longest known alpha decay half-life of any naturally occurring element. It is almost always considered on par with the 80 stable elements. The heaviest elements (those beyond plutonium, element 94) undergo radioactive decay with half-lives so short that they are not found in nature and must be synthesized. The number of the elements which are known today is 118. Out of them, 92 are present in the earth’s crust, and the remaining have been prepared artificially in the laboratory with the help of nuclear reactions. The number of manmade elements is likely to increase further. In the earth’s crust, the most abundant elements are oxygen (46.6%), silicon (27.7%), and aluminum (8.3%). The rest of the elements are present in smaller proportions.

History of Element

history of element

Many substances now known as elements have been known since ancient times. Gold (Au) was found and made into ornaments during the late stone age, some 10,000 years ago. More than 5,000 years ago, in Egypt, the metals iron (Fe), copper (Cu), silver (Ag), tin (Sn), and lead (Pb) were also used for various purposes.

Arsenic (As) was discovered around A.D. 1250, and phosphorus (P) was discovered around 1674. By 1700, about 12 elements were known, but they were not yet recognized as they are today.

The concept of elements—i.e., the theory that there are a limited number of fundamental pure substances out of which all other substances are made—goes back to the ancient Greeks.

Empedocles (c. 495–435 B.C.) proposed four basic “roots” of all materials: earth, air, fire, and water. Plato (c. 427–347 B.C.) referred to these four “roots” as stoicheia elements.

Aristotle (384–322 B.C.), a student of Plato’s, proposed that an element is “one of those simple bodies into which other bodies can be decomposed and which itself is not capable of being divided into others.” Except for nuclear fission and other nuclear reactions discovered more than 2,000 years later. The atoms of an element can be decomposed into smaller parts, and this definition remains accurate.

Several other theories were generated throughout the years, most of which have been dispelled. For example, the Swiss physician and alchemist Theophrastus Bombastus von Hohenheim (c. 1493–1541), also known as Paracelsus, proposed that everything was made of three “principles:” salt, mercury, and sulfur.

An alchemist named van Helmont (c. 1577–c.1644) tried to explain everything in terms of just two elements: air and water.

Eventually, English chemist Robert Boyle (1627–1691) revived Aristotle’s definition and refined it. In 1789, French chemist Antoine Lavoisier (1743–94) published a list of chemical elements that met Boyle’s definition.

Even though some of Lavoisier’s “elements” later turned out to be compounded (combinations of actual elements). His list set the stage for adopting standard names and symbols for the various elements.

The Swedish chemist J. J. Berzelius (1779–1848) was the first person to employ the modern method of classification: a one- or two-letter symbol for each element.

These symbols could be put easily together to show how the elements combine into compounds—for example, writing two Hs and one O together as H2O would mean that water’s particles (molecules) consist of two hydrogen atoms and one oxygen atom, bonded together.

Berzelius published a table of 24 elements, including their atomic weights, most of which are close to the values used today. By the year 1800, only about 25 true elements were known, but progress was relatively rapid throughout the nineteenth century.

By the time Russian scientist Dmitri Ivanovich Mendeleev (1834–1907) organized his periodic table in 1869, he had about 60 elements to reckon with.

In 1900 there were more than 80. The list quickly expanded to 92, ending at uranium (atomic number 92). There it stayed until 1940 when synthesis of the transuranium elements began.

Most of the remaining naturally occurring chemical elements were identified and characterized by 1900, including :

  • Such now-familiar industrial materials as aluminum, silicon, nickel, chromium, magnesium, and tungsten.
  • Reactive metals such as lithium, sodium, potassium, and calcium.
  • The halogens fluorine, chlorine, bromine, and iodine.
  • Gases such as hydrogen, oxygen, nitrogen, helium, argon, and neon.
  • Most of the rare-earth elements, including cerium, lanthanum, gadolinium, and neodymium.
  • The more common radioactive elements, including uranium, thorium, radium, and radon.

Elements isolated or produced since 1900 include

  • The three remaining undiscovered regularly occurring stable natural elements: hafnium, lutetium, and rhenium.
  • Plutonium, which was first produced synthetically in 1940 by Glenn T. Seaborg, but is now also known from a few long-persisting natural occurrences.
  • The three incidentally occurring natural elements (neptunium, promethium, and technetium). Which were all first produced synthetically but later discovered in trace amounts in certain geological samples.
  • Four scarce decay products of uranium or thorium, (astatine, francium, actinium, and protactinium), and various synthetic transuranic elements, beginning with americium and curium.

Types of Element

types of elements

Elements are further classified into three types on the basis of their physical state and properties. These are metals, non -metals and semi-metals.

Metals

metals in chemistry

Metals are solids (mercury is an exception and is liquid at room temperature) and usually are hard. They have luster, high melting, and boiling points and are also good conductors of heat and electricity.

In addition to these properties, metals are malleable(can be beaten into sheets) and ductile(can be drawn into wires).

It may be noted that the majority of the elements are metals. In chemistry, a metal is an element that readily forms positive ions (cations) and has metallic bonds.

Metals are sometimes described as a lattice of positive ions surrounded by a cloud of delocalized electrons.

The metals are one of the three groups of elements distinguished by their ionization and bonding properties, along with the metalloids and nonmetals.

On the periodic table, a diagonal line drawn from boron (B) to polonium (Po) separates the metals from the nonmetals.

Non Metals

non metals in chemistry

Non Metals are the elements with properties opposite to those of metals. They are found to be present in all three states of matter.

They do not possess lusture (iodine is an exception), are poor conductors of electricity(graphite is an exception), and are not malleable and ductile.

The common examples are hydrogen, Carbon, oxygen, nitrogen, etc.

Non-metals are the elements that form negative ions by accepting or gaining electrons. Non-metals usually have 4, 5, 6, or 7 electrons in their outermost shell.

Non metals are those which lack all the metallic attributes. They are good insulators of heat and electricity. They are mostly gases and sometimes liquid. Some of them are even solid at room temperatures like Carbon, sulfur, and phosphorus.

A chemical element (such as boron, Carbon, or nitrogen) that lacks metal properties and is capable of forming anions, acid oxides, acids, and stable hydrogen compounds.

Semi Metals

semi metals in chemistry

Semi Metals are the elements that have properties common with both metals and nonmetals. These are also called metalloids.

The common examples are of arsenic, antimony, and bismuth. Semimetals or metalloids are chemical elements that have properties of both metals and nonmetals.

Metalloids are important semiconductors, often used in computers and other electronic devices.

  • Metalloids are chemical elements that display properties of both metals and nonmetals.
  • On the periodic table, metalloids are found along a zig-zag line between boron and aluminum down to polonium and astatine.
  • Usually, the semimetals or metalloids are listed as boron, silicon, germanium, arsenic, antimony, tellurium, and polonium. Metalloids are used to make semiconductors, ceramics, polymers, and batteries.
  • Metalloids tend to be shiny, brittle solids that act as insulators at room temperature. But as conductors when heated or combined with other elements.

Some texts use the terms semimetals and metalloids interchangeably. Still, more recently, the preferred term for the element group is “metalloids”. So that “semimetals” may be applied to chemical compounds as well as elements that exhibit properties of both metals and nonmetals.

An example of a semimetal compound is mercury telluride (HgTe). Some conductive polymers may also be considered semimetals. Other scientists consider arsenic, antimony, bismuth, the alpha allotrope of tin (α-tin), and the graphite allotrope of carbon to be semimetals. These elements are also known as the “classic semimetals.”

Other elements also behave like metalloids, so the usual grouping of elements isn’t a hard-and-fast rule.

For example, carbon, phosphorus, and selenium exhibit both metallic and nonmetallic character. To some extent, this depends on the form or allotrope of the element. An argument could even be made for calling hydrogen a metalloid; it normally acts as a nonmetallic gas but can form a metal under certain circumstances.

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