What is molecules, atoms, atomic numbers?
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Atoms consist of protons and neutrons in a nucleus, with electrons in shells round it. \nIn an uncharged/neutral atom, the number of protons and electrons are equal and this is the same as the atomic number. In the periodic table, the elements are arranged in order of increasing atomic number. \nA molecule is two or more atoms chemically bonded together.\ne.g. Ne is an atom and H20 is a molecule.
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A compound is a material which is the chemical union of two or more different elements. The smallest possible division of a compound is a molecule. Molecules can be either compounds or made up of two or more atoms of the same element (common examples are the non-noble gases like hydrogen, H2 or oxygen, O2).
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The number of protons is equal to the number of electrons (unless it is an ion), but in this case they are equal. The atomic number is equal to the number of protons, and the mass number is the number of protons plus the number of neutrons.
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6.02 x 10^23 is the conversion for converting from moles to # of molecules or atoms.\n\nWhen you use the number 19, you are counting the number of atoms in a molecule, not the number of molecules in a mole.
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Use the periodic table of the elements.  The "weights" are in grams per mol.  Just use algebra and solve for the number of mols.  Then you know how many atoms there are by the number of mols which is a definite number.
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Atomic number\nThis was an idea by Mossely
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In scientific terms atoms are the smallest possible particle of a chemical element that retains its chemical properties. All atoms are made of the same basic elements, protons, neutrons and electrons , but each of the individual elements are made from different organizations of these materials. The basic structure of an atom is the nucleus, which is made of protons and neutrons (except hydrogen which only has a proton), and the electrons which, to over simplify it, "orbit" the nucleus. Elements are defined however by the number of protons in the nucleus, carbon always has 6 protons in it's nucleus, oxygen always has 8.\n\nAtoms are found EVERYWHERE. Everything you are, the air you breath, the things you smell, are all made of atoms, as others have said, it is the basic building block of everything, literally nothing would exist without them.\n\nIsotopes, contrary to what was said above, are in fact atoms, just a special kind of atom. The have the same amount of protons in their nucleus, hence they stay the same kind of element, but the have a different number of neutrons. I said above that hydrogen doesn't have a neutron in it's nucleus, and a standard hydrogen atom doesn't, but an isotope of hydrogen does, it's called deuterium, and it has 1 proton and 1 neutron in it's nucleus.\n\nDon't feel bad if you don't get it still, it really takes a class in chemistry to really get a handle on what exactly it all means. Good luck.
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Look on a periodic table.\n\nIt should be listed below the atomic number as a decimal value.  The mass number is an average mass (in atomic mass units) of an element, based on different isotopes.  It equals the number of protons + the number of neutrons in the nucleus.
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Atomic Number 3\nhttp://www.jergym.hiedu.cz/~canovm/vyhledav/varianty/litva.gif
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A proton, neutron, and electron is what makes up an atom.  a molecule however is defined as two or more atoms linked by chemical bonds which are linked atom.  Covalent bonds consist of shared pairs of electrons Electronegativity: unequal sharing of electrons...U can find more info on askjeeves.com
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An atom is the smallest chemical entity and the part of an element which preserves its chemical character. \n\nIts parts are Protons, Neutrons, Electrons.
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The atomic number is representative of the number of protons in the nucleus.  The atomic mass is representative of the number of total particles in the nucleus, which is made up solely of protons and neutrons.  That means that (35 total particles)-(17 protons)=18 neutrons.
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Quantum numbers are used to describe every single electron in an atom or molecule. Each electron is assigned it's own set of four different quantum numbers. no electron in the same atom or molecule can have the same set of quantum numbers.\n\nIn atoms:\nn = the principle quantum number. It is an integer, starting with 1, then 2, then 3, and so forth. This tells the principle energy level that the electron occupies. On the periodic table, the row number tells the higest principle quantum number an electron in that elemet can have. For example, the lone electron in hydrogen is always in the n = 1 energy level. However, an element like iodine in the 5th row can have electrons all the way up to the n + 5 energy level.\n\nl is the angular momentum quantum number. It is an integer that ranges from 0 to n-1. This number determines the shape of the electrons orbital. 0 is a sphere. 1 is dumbell shapped. 2 is two dumbells. 3 is 6 dumbells. These orbital shapes are usually represented with letters: 0 = s, 1 = p, 2 = d, 3 = f, 4 = g, and so on. s,p,d,f are the most commonly seen. Since l can range from 0 to n-1, n determines which orbital shapes the electrons in a given atom can have. In the first row, only s is possible. The second row adds p orbitals, and the third row adds d orbitals. Even though no atoms in the third row have occupied d orbitals in the ground state, they are still avaliable for bonding or excited state electrons (which explains why sulfer can and often does form more than 4 bonds)\n\nm is the magnetic quantum number. It simple tells the orientation of the orbitals. It ranges from -l to l. s orbitals have l = 0, so there is only one orientation. p orbitals have l = 1, so there are three, corresponding to m = -1, m= 0, and m = 1. d orbitals have 5 orientations, and f orbitals have 7. The number of orientations is also equal to the number of each type of orbital an atom (1 s orbital, 3 p orbitals, 5 d orbitals, 7 f orbitals) per energy level.\n\nm sub s (written as an m with a subscript s) is thespin quantum number. Every orbital can hold two electrons, however due to Pauli's Exclusion Principle, they can't have the same set of quantum numbers. The spin quantum number is either +1/2 or - 1/2, and it determines the direction of the electron's "spin." This isn't spin in the normal sense, as electrons don't spin like tops.
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A more generic term for the components of an atom is "sub-atomic particles."  I think that's the answer you're looking for.
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An atom is the smallest unit of a chemical.\n\nA cell is the smallest unit of a living thing.\n\nFor more detailed infomration see the links.
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ATOM..basic building block\n \n[Gr.,=uncuttable (indivisible)], basic unit of matter; more properly, the smallest unit of a chemical element having the properties of that element.  That is the definition.  Continue to read further; it really gives great detail!!!!!\n\nStructure of the Atom\n\nThe atom consists of a central, positively charged core, the nucleus, and negatively charged particles called electrons that are found in orbits around the nucleus.\n\nThe Nucleus\n\nAlmost the entire mass of the atom is concentrated in the nucleus, which occupies only a tiny fraction of the atom's volume. The nucleus of an atom consists of neutrons and protons, the neutron being an uncharged particle and the proton a positively charged one. Their masses are almost equal. Atoms containing the same number of protons but different numbers of neutrons represent different forms, or isotopes, of the same element.\n\nThe Electrons\n\nSurrounding the nucleus of an atom are its electrons; for a neutral atom, the number of electrons is equal to the atomic number. The outermost electrons of an atom determine its chemical and electrical properties. An atom may combine chemically with another atom in various ways, either by giving up or receiving electrons, thus setting up an electrical attraction between the atoms (see ion), or by sharing one or more pairs of electrons (see chemical bond). Because metals have few outermost electrons and tend to give them up easily, they are good conductors of electricity or heat (see conduction).\n\nThe electrons are often described as revolving about the nucleus as the planets revolve about the sun. This picture, however, is misleading. The quantum theory has shown that all particles in motion also have certain wave properties. For a particle the size of an electron, these properties are of considerable importance. As a result the electrons in an atom cannot be pictured as localized in space, but rather should be viewed as smeared out over the entire orbit so that they form a cloud of charge. The electron clouds around the nucleus represent regions in which the electrons are most likely to be found. The shapes of these clouds can be very complex, in marked contrast to the simple elliptical orbits of planets. Surprisingly, the sizes of all atoms are comparable, in spite of the large differences in the number of electrons they contain.\n\nAtomic Weight and Number\n\nThe atomic number of an atom is simply the number of protons in its nucleus. The atomic weight of an atom is given in most cases by the mass number of the atom, equal to the total number of protons and neutrons combined. An atom may be conveniently symbolized by its chemical symbol with the atomic number and mass number written as subscript and superscript, respectively. For example, the symbol for uranium is U (atomic number 92); the isotopes of uranium with atomic weights 235 and 238 are indicated by 23592U and 23892U.\n\nDevelopment of Atomic Theory\n\nEarly Atomic Theory\n\nThe atomic theory, which holds that matter is composed of tiny, indivisible particles in constant motion, was proposed in the 5th cent. by the Greek philosophers Leucippus and Democritus and was adopted by the Roman Lucretius. However, Aristotle did not accept the theory, and it was ignored for many centuries. Interest in the atomic theory was revived during the 18th cent. following work on the nature and behavior of gases (see gas laws).\n\nFrom Dalton to the Periodic Table\n\nModern atomic theory begins with the work of John Dalton, published in 1808. He held that all the atoms of an element are of exactly the same size and weight (see atomic weight) and are in these two respects unlike the atoms of any other element. He stated that atoms of the elements unite chemically in simple numerical ratios to form compounds. The best evidence for his theory was the experimentally verified law of simple multiple proportions, which gives a relation between the weights of two elements th
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Molecules always refer to atoms that have covalent bonds (like a water molecule). Stuff with ionic bonds are just ionic compounds.\n\nMore info: http://misterguch.brinkster.net/covalentcompounds.html