What Is The Makeup Of Elements Called
What is an atom? Facts virtually the edifice blocks of the universe
Atoms are the basic units of matter. Everything in the universe apart from energy is made of thing therefore atoms make upwardly everything in the universe, according to Northwestern University. The term "atom" comes from the Greek word for indivisible, because it was in one case thought that atoms were the smallest things in the universe and could not exist divided. We now know that atoms are made upwards of three particles known every bit subatomic particles: protons, neutrons and electrons — which are equanimous of even smaller particles, such every bit quarks.
Atoms were created subsequently the Large Blindside xiii.7 billion years agone. As the hot, dumbo new universe cooled, conditions became suitable for quarks and electrons to grade. Quarks came together to course protons and neutrons, and these particles combined into nuclei. This all took place inside the offset few minutes of the universe's existence, according to CERN.
It took 380,000 years for the universe to cool enough to irksome downward the electrons so that the nuclei could capture them to grade the first atoms. The primeval atoms were primarily hydrogen and helium, which are still the most abundant elements in the universe, according to Jefferson Lab. Gravity eventually caused clouds of gas to coagulate and grade stars, and heavier atoms were (and still are) created within the stars and sent throughout the universe when the star exploded (supernova).
Related: What is antimatter, how is information technology fabricated and is it unsafe?
Diminutive particles
Protons and neutrons are heavier than electrons and reside in the nucleus at the eye of the atom. Electrons are extremely lightweight and exist in a cloud orbiting the nucleus. The electron cloud has a radius 10,000 times greater than the nucleus, co-ordinate to the Los Alamos National Laboratory.
Protons and neutrons take approximately the aforementioned mass. Nonetheless, ane proton is about one,835 times more than massive than an electron. Atoms e'er have an equal number of protons and electrons, and the number of protons and neutrons is usually the aforementioned as well. Calculation a proton to an atom makes a new chemical element, while adding a neutron makes an isotope, or heavier version, of that cantlet.
Nucleus
The nucleus was discovered in 1911 by Ernest Rutherford, a physicist from New Zealand, according to the American Institute of Physics. In 1920, Rutherford proposed the name proton for the positively charged particles of the cantlet. He too theorized that there was a neutral particle within the nucleus, which James Chadwick, a British physicist and pupil of Rutherford'southward, was able to ostend in 1932.
Almost all the mass of an cantlet resides in its nucleus, according to Chemistry LibreTexts. The protons and neutrons that make up the nucleus are approximately the same mass (the proton is slightly less) and have the same angular momentum, or spin.
The nucleus is held together by the strong force, one of the 4 bones forces in nature. This force between the protons and neutrons overcomes the repulsive electrical force that would otherwise button the protons apart, according to the rules of electricity. Some diminutive nuclei are unstable because the binding forcefulness varies for different atoms based on the size of the nucleus. These atoms volition then decay into other elements, such as carbon-14 decomposable into nitrogen-14.
Protons
Protons are positively charged particles found within atomic nuclei. Rutherford discovered them in experiments with cathode-ray tubes that were conducted between 1911 and 1919. Protons are about 99.86% every bit massive as neutrons according to the Jefferson Lab.
The number of protons in an atom is unique to each element. For example, carbon atoms have six protons, hydrogen atoms take one and oxygen atoms have eight. The number of protons in an atom is referred to as the diminutive number of that chemical element. The number of protons likewise determines the chemical behavior of the element. Elements are bundled in the Periodic Tabular array of the Elements in lodge of increasing diminutive number.
3 quarks make up each proton — ii "up" quarks (each with a 2-thirds positive charge) and one "down" quark (with a one-third negative accuse) — and they are held together by other subatomic particles called gluons, which are massless.
Electrons
Electrons are tiny compared to protons and neutrons, over ane,800 times smaller than either a proton or a neutron. Electrons are about 0.054% as massive as neutrons, according to Jefferson Lab.
Joseph John (J.J.) Thomson, a British physicist, discovered the electron in 1897, according to the Science History Plant. Originally known as "corpuscles," electrons have a negative accuse and are electrically attracted to the positively charged protons. Electrons surround the atomic nucleus in pathways called orbitals, an idea that was put forth by Erwin Schrödinger, an Austrian physicist, in the 1920s. Today, this model is known equally the breakthrough model or the electron deject model. The inner orbitals surrounding the atom are spherical but the outer orbitals are much more than complicated.
An atom'due south electron configuration refers to the locations of the electrons in a typical cantlet. Using the electron configuration and principles of physics, chemists can predict an atom's backdrop, such every bit stability, boiling point and conductivity, co-ordinate to the Los Alamos National Laboratory.
Related: What is quantum entanglement?
Neutrons
The neutron's being was theorized by Rutherford in 1920 and discovered by Chadwick in 1932, according to the American Physical Society. Neutrons were establish during experiments when atoms were shot at a thin sheet of beryllium. Subatomic particles with no charge were released — the neutron.
Neutrons are uncharged particles found within all atomic nuclei (except for hydrogen). A neutron'south mass is slightly larger than that of a proton. Like protons, neutrons are also made of quarks — one "up" quark (with a positive 2/3 charge) and 2 "downward" quarks (each with a negative ane-tertiary accuse).
History of the atom
The theory of the atom dates at to the lowest degree as far dorsum as 440 B.C. to Democritus, a Greek scientist and philosopher. Democritus almost likely built his theory of atoms upon the work of by philosophers, co-ordinate to Andrew G. Van Melsen, writer of "From Atomos to Atom: The History of the Concept Atom" (Duquesne University Press, 1952).
Democritus' explanation of the atom begins with a stone. A stone cutting in half gives two halves of the same rock. If the stone were to be continuously cutting, at some point at that place would exist a slice of the rock small enough that it could no longer be cut. The term "atom" comes from the Greek word for indivisible, which Democritus concluded must be the point at which a being (any form of affair) cannot be divided any more than, according to educational website Lumen Learning.
His explanation included the ideas that atoms be separately from each other, that there are an space amount of atoms, that atoms are able to move, that they can combine together to create matter only do not merge to become a new atom, and that they cannot exist divided, co-ordinate to Universe Today. However, considering most philosophers at the time — especially the very influential Aristotle — believed that all matter was created from earth, air, burn down and water, Democritus' atomic theory was put aside.
John Dalton, a British chemist, built upon Democritus' ideas in 1803 when he put forth his ain atomic theory, according to the chemistry section at Purdue University. Dalton'southward theory included several ideas from Democritus, such as atoms are indivisible and indestructible and that different atoms form together to create all matter. Dalton's additions to the theory included the following ideas: That all atoms of a certain element were identical, that atoms of one element will have different weights and properties than atoms of some other element, that atoms cannot be created or destroyed and that matter is formed by atoms combining in elementary whole numbers.
Thomson, the British physicist who discovered the electron in 1897, proved that atoms can exist divided, according to the Chemical Heritage Foundation. He was able to decide the existence of electrons by studying the properties of electrical discharge in cathode-ray tubes. Co-ordinate to Thomson's 1897 paper, the rays were deflected within the tube, which proved that there was something that was negatively charged within the vacuum tube.
In 1899, Thomson published a description of his version of the atom, commonly known every bit the "plum pudding model." An excerpt of this newspaper is found on the Chem Team site. Thomson'due south model of the atom included a large number of electrons suspended in something that produced a positive charge giving the atom an overall neutral charge. His model resembled plum pudding, a popular British dessert that had raisins suspended in a round cake-like ball.
The next scientist to further modify and accelerate the atomic model was Rutherford, who studied under Thomson, according to the chemistry department at Purdue University. In 1911, Rutherford published his version of the atom, which included a positively charged nucleus orbited by electrons. This model arose when Rutherford and his assistants fired alpha particles at sparse sheets of gilded. An alpha particle is fabricated up of two protons and two neutrons, all held together by the same strong nuclear force that binds the nucleus, according to the Jefferson Lab.
The scientists noticed that a pocket-sized percentage of the blastoff particles were scattered at very large angles to the original direction of motion while the majority passed right through hardly disturbed. Rutherford was able to guess the size of the nucleus of the golden atom, finding information technology to exist at to the lowest degree x,000 times smaller than the size of the unabridged atom with much of the atom existence empty infinite. Rutherford's model of the atom is all the same the basic model that is used today.
Several other scientists furthered the diminutive model, including Niels Bohr (built upon Rutherford's model to include properties of electrons based on the hydrogen spectrum), Erwin Schrödinger (adult the quantum model of the atom), Werner Heisenberg (stated that one cannot know both the position and velocity of an electron simultaneously), and Murray Gell-Mann and George Zweig (independently developed the theory that protons and neutrons were composed of quarks).
Additional resources
- Read more near the early universe, from CERN.
- Learn more about the history of atomic chemical science in this video from Khan University.
- Check out this usefultive slide show about atoms from the Jefferson Lab.
Source: https://www.livescience.com/37206-atom-definition.html
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