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An atom is the smallest particle of an element that has the same properties as the element. It consists of a nucleus of protons and neutrons, and electrons that orbit around it. Learn more about the history of atomic theory and the structure of atoms.
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- Atomic model
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An atom is the basic building block of chemistry. It is the smallest unit into which matter can be divided without the release of electrically charged particles. It also is the smallest unit of matter that has the characteristic properties of a chemical element.
Are all atoms the same size?
All atoms are roughly the same size, whether they have 3 or 90 electrons. Approximately 50 million atoms of solid matter lined up in a row would measure 1 cm (0.4 inches). A convenient unit of length for measuring atomic sizes is the angstrom, defined as 10−10 meters.
What does the mass of an atom consist of?
The mass of an atom consists of the mass of the nucleus plus that of the electrons. That means the atomic mass unit is not exactly the same as the mass of the proton or neutron.
How is the atomic number of an atom defined?
Most matter consists of an agglomeration of molecules, which can be separated relatively easily. Molecules, in turn, are composed of atoms joined by chemical bonds that are more difficult to break. Each individual atom consists of smaller particles—namely, electrons and nuclei. These particles are electrically charged, and the electric forces on the charge are responsible for holding the atom together. Attempts to separate these smaller constituent particles require ever-increasing amounts of energy and result in the creation of new subatomic particles, many of which are charged.
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As noted in the introduction to this article, an atom consists largely of empty space. The nucleus is the positively charged centre of an atom and contains most of its mass. It is composed of protons, which have a positive charge, and neutrons, which have no charge. Protons, neutrons, and the electrons surrounding them are long-lived particles present in all ordinary, naturally occurring atoms. Other subatomic particles may be found in association with these three types of particles. They can be created only with the addition of enormous amounts of energy, however, and are very short-lived.
Learn about the basic building block of matter and chemistry, composed of protons, neutrons, and electrons. Explore the atomic model, the periodic table, and the history of atomism.
Nov 19, 2023 · An atom is the basic building block of matter, consisting of protons, neutrons, and electrons. Learn about the structure, properties, and history of atoms, as well as the differences between matter and antimatter atoms.
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Molecules are made when two or more atoms chemically bond together. Atoms from different elements can combine. When the atoms are from different elements, the molecule can also be called...
Dec 15, 2021 · Atoms are the basic units of matter made of protons, neutrons and electrons. Learn how atoms were created after the Big Bang, how they are arranged in the Periodic Table and what are their subatomic particles.
Jan 24, 2024 · Learn how atoms are the tiny building blocks of everything around us, and what subatomic particles make up their structure. Find out how atoms of different elements differ in size, shape, and number of protons, neutrons, and electrons.
Oct 30, 2022 · Learn what atoms are, how they are built from protons, neutrons and electrons, and how they form the elements in the Periodic Table. Explore the discovery of the atom, radioactive decay, ionization and more.
