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7-1, 7-2, 7-3, 7-4, 7-5, 7-6, 7-7, 7-8, 7-9, 7-10, 7-12, 7-13
Lavoisier stated the law of conservation of mass
Democritus said world was made up of empty space and atoms Aristotle opposed this theory/Newton and Boyle supported this theory
John Dalton(1800's) proposed IN ORDINARY CHEMICAL REACTIONS, MATTER CAN BE CHANGED IN MANY WAYS, BUT IT CANNOT BE CREATED OR DESTROYED(law conservation of mass)
Joseph Proust said SPECIFIC SUBSTANCES ALWAYS CONTAIN ELEMENTS IN THE SAME RATIO BY MASS(law definite proportions) BACK TO TOP OF PAGE
All matter is composed of small particles called atoms; atoms of an element are exactly alike; atoms can unite with other atoms in simple ratios to form compounds. ATOMIC THEORY
Not all atoms of same element have the same mass therefore "atoms of the same element my differ in mass. thus, the term average mass is used rather than the term mass."
Law of multiple proportions THE RATIO OF MASSES OF ONE ELEMENT THAT COMBINE WITH A CONSTANT AMOUNT OF ANOTHER ELEMENT CAN BE EXPRESSED IN SMALL WHOLE NUMBERS
Avogadro-equal volumes of gases, under the same conditions have the same number of molecules
Gay-Lussac-under constant conditions, the volumes of reacting gases and gaseous products are in the ratio of small whole numbers. BACK TO TOP OF PAGE
7-3 Early Research on Atomic Particles
Positive electrode is ANODE; negative electrode is CATHODE
JJ Thompson discovered that rays consist of electrons
Milikan discovered the charge on the electron(1.6 x 10-19 C) the mass of an electron is 9.1 x10-31 kg
The charge on an electron e- is -1/the proton has an equal but opposite charge, p+, +1; and its mass is 1836 times that of an electron.
Chadwick discovered the neutron, n0, no charge
Nobel Prize in Physics was awarded to JJ Thompson(1906), Robert Millikan(1923), James Chadwick(1935) for their research on atomic particles.
Modern atomic theory differs from Daltons atomic theory due to the discovery of subatomic particles and isotopes BACK TO TOP OF PAGE
7-4 Isotopes and atomic number
Atoms of the same element that differ in mass are called isotopes
Isotopes have the same number of protons but different number of neutrons.
Number of protons is called ATOMIC NUMBER of element/since atoms are neutral it has the same number of electrons.
The number of protons determines the identity of the element and the number of neutrons determines the particular isotope of the element.
Particles that make up the atomic nucleus are called nucleons and are protons and neutrons. The total number of nucleons in an atom is called the MASS NUMBER
Mass number-atomic number=number of neutrons in atom BACK TO TOP OF PAGE
Rutherford showed that the atom has a central positive nucleus surrounded by electrons.
An atom is mostly space. In a baseball stadium if the center of the field is the nucleus the first electron will be found in the last row of seats.
More than 99.9% of an atom's mass is in its nucleus
A cubic inch of nuclear matter would weigh about a billion tons BACK TO TOP OF PAGE
7-6 Radioactivity(add to section)
When atomic particles escape an atom due to nuclear disintegration this is called radioactivity.
Einstein E=mc2 matter can be changed into energy
Radioactive decay is spontaneous, it cannot be controlled
Stable means unchanging/most atoms are stable
Small number of atoms are unstable, they change(decay) and are called radioactive BACK TO TOP OF PAGE
Protons and neutrons are held together by a nuclear force
The particles composing atoms are called subatomic particles
Leptons are light(not heavy) particles the electron is an example
Hadrons are small complex particles the neutron and proton are examples
A mirror-image antiparticle exists, or is believed to exist, for every particle
The rest of the particle in the book are interesting to read about but we will concentrate on electrons, neutrons, and protons-Chemistry as you will study it can be fully explained and understood using these basic particles
Some 200 particles have been "found" BACK TO TOP OF PAGE
Alpha particle-is a helium nucleus/2 protons and 2 neutrons/has a charge of +2 and is the heaviest of the radioactive particles
Beta Particle-is an electron/has a charge of -1/ and is light in weight
Gamma particle-are very high energy X rays
A gamma ray photon may carry a million times more energy than a visable photon- gamma does not necessary change the atom
BACKGROUND RADIATION AND NATURAL RADIATION
RADIATION SICKNESS BACK TO TOP OF PAGE
MODEL OF ATOM called the planetary atomic model because it describes electron in "orbit" around the nucleus
Visible light;radio waves;uv waves;x rays are electromagnetic energy/visable light made of colors ROYGBIV
Frequency-the number of oscillations per second(crest to crest) measured in c/s or hz(1c/s=1hz)
wavelength-distance between crest to crest(or trough to trough)
VELOCITY=FREQUENCY TIMES WAVELENGTH/ the speed of light is 186,282 miles per second
amplitude-the distance between the midpoint to the crest or trough
crest-top of wave
trough-bottom wave
AM-amplitude modulation(change)
FM-frequency modulation
Spectroscopy-an instrument that spreads the colors or wavelengths of light for visual observation is called a spectroscope. If you record the spectrum on a piece of film it is called a spectrograph. Every atom has it own unique spectrum-we use this to identify lements.
The energy emitted by gaseous atoms can be spread into an emission spectrum
The lines missing in an absorption spectrum will be the same as the bright lines in the emission spectrum(see PG 129 F7-18) BACK TO TOP OF PAGE
There were two theories of light/wave theory and energy(photon) theory. Scientists argued for years which were right.
Planck combined both by the formula E=hv / h is planck constant
Planck proposed that light travels in small packets called photons
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7-11 skip
Nearly all of the mass of an atom is in the nucleus
Chemists generally work with moles of atoms rather than individual atoms.
1 mole is the number of atoms equal to the avogadro constant (6.023 X 1023)
An amu(atomic mass unit) is equal to 1/12 the mass of carbon 12(carbon 12 was selected as the standard because of its isotopic purity)
electron=9.10953 X 10-28 g = .000549 u
Proton= 1.67265 X 10-24 g = 1.0073 u
neutron= 1.67495 X 10-24 g = 1.0087 u BACK TO TOP OF PAGE
The average atomic mass of an element is used in calculations
A mass spectrometer measures the masses and amounts of the nuclides of elements
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