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18 Cards in this Set

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This guy first used the term atom to descrive the smallest unit of matter
Law of Conservation of Mass
Lavoisier: the total mass before a chemical change is the same as after a chemical change.
Law of Definite Composition(/Proportion)
Proust: In a given compound, the relative number and kinds of atoms are constant OR in a given compound, there is always present the same proportion of elements by mass
4 points of Dalton's Atomic Theory
1. All elements are composed of small, indivisible particles called atoms.
2. Atoms of a given element are identical. Atoms of diff. elements are diff. and have diff. properties.
3. In a chemical rxn atoms are neither created nor destroyed.
4. When 2 or more elements combine, a compound is formed. Compounds always have the same relative # and kids of atoms.
Which of Dalton's 4 points is/are wrong?
1. atoms are indivisible. Nuclear fusion/fission
2. Atoms of a given element are identical. isotopes.
Law of Multiple Proportions
If 2 or more compounds are composed of the same 2 elements, the ration of the masses of the 2nd element combines w/ a certain mass of the 1st element is always a ration of small whole #'s.
He discovered the election and proposed to plum pudding atomic
J.J. Thomson
His work on cathode rays showed that electrons were negatively charged.
William Crooke
From his famous gold foil experiment, he concluded that an atom is mostly empty space with a small, dense, positively charged nucleus

(mass of a proton is 1amu/dalton)
He is credited with discovering the neutron.
James Chadwick
proposed that electrons orbit the nucleus similar to the way the planets revolve around the Sun (wrong)

the ____ of atom
Niehls Bohr
The modern atom is called
-electron cloud
-quantum cloud-model
In the electron cloud , what is special about the electrons?
We can only predict the probability of finding an electron in a certain area at a certain time.
What non-SI unit do scientists often use to give atomic diameters?
angstrom = 10^-10 m
We can never at any given time give an electron's exact location and speed. We can only predict the probability of where it is at any given moment is called the...
Heisenberg Uncertainty Principle.
Define proton
+ charged particles located in the nucleus. Mass is approximately 1 amu.
Define Neutron
neutral particle located in the nucleus. The mass of a neutron is approximately 1 amu.
Define Electron
- charged particle located in area around the nucleus. Mass of electrons is negligible (fairly insignificant)