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An atom consists of a small, heavy nucleus surrounded by a relatively large, light cloud of electrons. An atomic nucleus consists of 1 or more protons and 0 or more neutrons. Protons and neutrons are, in turn, made of quarks. Each type of atom corresponds to a specific chemical element. To date, 118 elements have been discovered or created.
A table or chart of nuclides is a two-dimensional graph of isotopes of the elements, in which one axis represents the number of neutrons (symbol N) and the other represents the number of protons (atomic number, symbol Z) in the atomic nucleus. Each point plotted on the graph thus represents a nuclide of a known or hypothetical chemical element.
This is an index of lists of molecules (i.e. by year, number of atoms, etc.). Millions of molecules have existed in the universe since before the formation of Earth. Three of them, carbon dioxide, water and oxygen were necessary for the growth of life.
Hydrogen is the element with atomic number 1; helium, atomic number 2; lithium, atomic number 3; and so on. Each of these names can be further abbreviated by a one- or two-letter chemical symbol; those for hydrogen, helium, and lithium are respectively H, He, and Li. [6] Neutrons do not affect the atom's chemical identity, but do affect its weight.
The number of protons (Z column) and number of neutrons (N column). energy column The column labeled "energy" denotes the energy equivalent of the mass of a neutron minus the mass per nucleon of this nuclide (so all nuclides get a positive value) in MeV , formally: m n − m nuclide / A , where A = Z + N is the mass number.
Neutrons are made up of one up and two down quarks, while protons are made of two up and one down quark. Since the other common elementary particles (such as electrons, neutrinos, or weak bosons) are so light or so rare when compared to atomic nuclei, we can neglect their mass contribution to the observable universe's total mass.
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
The electrons of an atom are attracted to the protons in an atomic nucleus by the electromagnetic force. The protons and neutrons in the nucleus are attracted to each other by the nuclear force. This force is usually stronger than the electromagnetic force that repels the positively charged protons from one another.