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16 Cards in this Set
- Front
- Back
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Democritus work? |
460 to 370bc . Called particles atomos derived from the word "atoms" means indivisible. |
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Contributions of John Dalton |
In 1808 an English school teacher John Dalton recognized that the law of conservation of matter and the law of definite proportions could be explained by the existence of atoms . He developed an atomic theory Tha main postulates of which that "All matter is composed of atoms of different elements, Which differ in their properties". |
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Define atom |
Smallest particle of element which may or may not exist independently and can take part in a chemical reaction. May exist(stable atom): He, Ne ,At,kr, Xe ,Rn May not exist independently (unstable atom): Na, Cl, Ca, O,Al |
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What is the composition of atoms? |
The modern researchers have shown that an atom is composed of subatomic particles like *Electron *Proton * Neutron *Hypron *Neutrino *Anti neutrino However protons electrons and neutrons are regarded as fundamental particles of atoms |
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Contributions of Jacob Berzelius? |
(1779-1848) *Determined the atomic masses of elements * A number of his values are close to the modern values of atomic masses. * Berzelius also developed a system of giving element a symbol. |
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Ordinary optical microscope can measure the size of an object up to ? |
500nm (1nm=10 `-9m) |
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Why can electron microscope observe objects of the size of an atom? |
Electron microscope uses beams of electrons instead of visible light, because wavelengths of electron is much shorter than that of visible light . Example:piece of graphite which has been magnified upto 15 mill ion times . The bright bands in the figure are the layers of carbon atoms. |
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Diameter of atoms? In nanometer ? In angstrom? In pico meter? |
2×10'-10m which is 0.2 nm *2 angstrom *1 angstrom = 10'-10 *200pm (2×100×10'12) |
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Radius of atom? |
*1×10'-10 *1 angstrom *0.1nm ( 10'-9 m=1nm) *100 pico meter |
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Mass of atom? |
10'-27 to 10'-25 kg range |
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1amu= |
1.661×10'-27kg |
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One full stop contains how many atoms? |
2 million |
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Define molecule? |
A molecule is the smallest particle of a pure substance which may be atom or a group of atoms which can exist independently. NOBLE GASES: He, Ne, Ar, kr,Xe,Rn GROUP OF ATOMS: H2, H2O, CO2 |
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Atomicity? |
The number of atoms present in a molecule determines its atomicity. *Monoatomic: Containing one atom. E.g: He, Ne,Ar, Kr,Xe,Rn * Diatomic: Containing two atoms .eg: HCl ,O2 H2 *Triatomic: Containing three atoms .eg: H20, C02 |
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Percentage in of an element? |
the percentage of an element in a compound is the number if grams of that element present in 100 grams of the compound. |
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The size of the molecule depends upon ? |
The number of atoms present in them and their shapes . ( Atomicity and molecular weight) |
