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Test 2--Scientists and Conversions
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30
Chemistry
11th Grade
11/03/2010

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Term
Democritus
Definition
400 BC
Founded Atoms
Called them indivisible.
Term
Aristotle
Definition
Refuted atoms.
Thought that all matter was continuous.
Term
Law of Conservation of Mass
Definition
Mass is neither destroyed nor created during ordinary chemical or physical reactions.
Term
Law of Definite Proportions
Definition
A chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound.
Term
Law of Multiple Proportions
Definition
If two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers.
Term
John Dalton
Definition
1808
Explained the law of conservation of mass, law of definite proportions and the law of multiple proportions.
Term
Dalton's Atomic Theory
Definition
1. All matter is composed of extremely small particles called atoms.
2. Atoms of a given element are identical size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
3. Atoms can not be subdivided, created, or destroyed.
4. Atoms of different elements combine in simple, whole number ratios to form chemical compounds.
5. In chemical reactions, atoms are combined, separated, or rearranged.
Term
Two of Dalton's Points Proven Wrong
Definition
Atoms ARE divisible into smaller particles.
A given element can have atoms with different masses.
Term
Atom
Definition
Smallest particle of an element that retains the chemical properties of that element.
Term
Joseph John Thompson
Definition
Founded electrons by observing cathode ray tubes.
Term
Robert A. Millikan
Definition
Found that the electron is much much smaller than the smallest atom of an element.
Also discovered that the electron has a negative charge.
Term
Atomic Structure Inferences
Definition
1. Because atoms are electrically neutral, they must contain a positive charge to balance the negative electrons.
2. Because electrons have so much less mass than atoms, atoms must contain other particles that account for most of their mass.
Term
Ernst Rutherford, Hans Geiger and Ernest Marsden
Definition
Founded the nucleus of the atom.
Also founded the electron cloud.
Term
Nuclear Forces
Definition
Short range proton-neutron, proton-proton, and neutron-neutron forces hold the nuclear particles together.
Term
Atomic Number
Definition
Number of protons in a nucleus of each atom of that element.
Term
Isotopes
Definition
Atoms of the same element that have different masses.
Term
Mass number
Definition
total number of protons and neutrons in the nucleus of an isotope.
Term
Nuclide
Definition
General term for any isotope for any element.
Term
Atomic Mass Unit (Amu)
Definition
The unit that is equal to the mass of carbon-12 and is used as a relative measurement of the periodic table.
Term
Average Atomic Mass
Definition
the weighted average of the atomic masses of the naturally occurring isotopes of that element.
Term
Mole
Definition
Amount of a substance that contains as many particles as there are atoms in exactly 12g of carbon-12.
Term
Avogadro's Number
Definition
(6.022 X10tothe23rd) the number of particles in exactly one mole of a pure substance.
Term
Molar Mass
Definition
The mass of one mole of a pure substance.
Term
Moles-->Atoms
Definition
Amt. of element in moles X 6.022x1023=Number of atoms.
Term
Atoms-->Moles
Definition
Number of atoms X 1/6.022x1023=Moles
Term
Atoms-->Mass
Definition
Number of atoms X 1/(6.022x1023) X molar mass of element=Mass in grams.
Term
Mass-->Atoms
Definition
Mass of element X 1/Molar Mass of element x(6.022x1023)=Atoms
Term
Mass-->Moles
Definition
Mass of element x 1/molar mass of element=Moles
Term
Moles-->Mass
Definition
Moles X molar mass of element = Mass of element
Term
Conversion Numbers
Definition
1 mole=6.022X1023 atoms
1 mole= molar mass of element
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