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Lavoisier. Law of conservation of mass Matter is neither created or destroyed during ordinary chemical reactions. . Proust. Law of Definite Proportions A chemical compound contains the same elements in the same proportions regardless of size of the sample or source of the compound .
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Lavoisier • Law of conservation of mass • Matter is neither created or destroyed during ordinary chemical reactions.
Proust • Law of Definite Proportions • A chemical compound contains the same elements in the same proportions regardless of size of the sample or source of the compound
Dalton’s Atomic Theory 1. Matter is composed of __atoms____ 2. Atoms of the same element are __identical__. Atoms of different elements are _different__. 3. Atoms can not be _subdivided_, _created__ __destroyed__. 4. Atoms of different elements combine in simple _whole___ _number_ ratios to form chemical compounds. In chemical reactions, atoms are _combined__, _separated_, or _rearranged_.
JJ Thomson Cathode Ray Tube Discovery of the electron. Atoms are composed of smaller particles Plum Pudding model
Rutherford • Gold Foil Experiment • Conclusions… • 1. Each atom contains a small dense, positively charged nucleus. • 2. Atoms are mostly empty space.
Bohr Model of the Atom Electrons must be in orbitals around the nucleus
The Bohr Model of the Atom • e- can only exist in certain discrete orbits • Electrons moving from a higher to a lower state create different colors of light • Higher energy is blue • Lower energy is red
H Hg Ne The Atomic Spectra Heated element is emitted is light spectra when focused through prism • Each element has its own, unique spectrum
Light Waves • Wavelength (λ) is the distance light travels in one cycle. • Frequency (f) is the number of wave cycles completed each second. • Amplitude is the height measured from the center of the wave.
The Wave Nature of Light • Speed of a wave, c, is given by its frequency multiplied by its wavelength: • For light, speed = c = 3.00x108m/s or 3x1017 nm/s
Frequency - Wavelength The red light in a laser pointer comes from a laser that has a wavelength of 6.32 x 10-7 m. What is the frequency of the light?
Quantized energy • Planck: energy can be absorbed or released from atoms in particles called quanta or photons • The energy of one photon is • E=h f h=6.63 x 10-34 J s
Energy of Emission For red light with a wavelength of about 6.32 x 10-7 m, what is the energy of a single photon?