AP Chemistry Electronic Structure of Atoms electronic structure

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AP Chemistry Electronic Structure of Atoms electronic structure: the arrangement of electrons in an

AP Chemistry Electronic Structure of Atoms electronic structure: the arrangement of electrons in an atom quantum mechanics: the physics that correctly describes atoms ?

electromagnetic radiation (i. e. , light) -- waves of oscillating electric (E) and magnetic

electromagnetic radiation (i. e. , light) -- waves of oscillating electric (E) and magnetic (B) fields -- source is… vibrating electric charges E B

Characteristics of a Wave crest amplitude A trough wavelength l frequency: the number of

Characteristics of a Wave crest amplitude A trough wavelength l frequency: the number of cycles per unit time (usually sec) -- unit is Hz, or s– 1

electromagnetic spectrum: contains all of the “types” of light that vary according to frequency

electromagnetic spectrum: contains all of the “types” of light that vary according to frequency and wavelength 750 nm 400 nm -- visible spectrum ranges from only ~400 to 750 nm (a very narrow band of spectrum) cosmic rays gamma rays X-rays UV low energy visible low f IR microwaves radio waves large l ROYGBV small l high f high energy

Albert Michelson (1879) -- first to get an accurate value for speed of light

Albert Michelson (1879) -- first to get an accurate value for speed of light Albert Michelson (1852– 1931) The speed of light in a vacuum (and in air) is constant: c = 3. 00 x 108 m/s -- Equation: c=nl=fl

In 1900, Max Planck assumed that energy can be absorbed or released only in

In 1900, Max Planck assumed that energy can be absorbed or released only in certain discrete amounts, which he called quanta. Later, Albert Einstein dubbed a light “particle” that carried a quantum of energy a photon. -- Equation: Max Planck (1858– 1947) E=hn=hf E = energy, in J h = Planck’s constant = 6. 63 x 10– 34 J-s (i. e. , J/Hz) Albert Einstein (1879– 1955)

A radio station transmits at 95. 5 MHz (FM 95. 5). Calculate the wavelength

A radio station transmits at 95. 5 MHz (FM 95. 5). Calculate the wavelength of this light and the energy of one of its photons. 3. 00 x 108 m/s = 3. 14 m = 6 95. 5 x 10 Hz c=fl E = h f = 6. 63 x 10– 34 J/Hz (95. 5 x 106 Hz) = 6. 33 x 10– 26 J

In 1905, Einstein explained the photoelectric effect using Planck’s quantum idea. -- only light

In 1905, Einstein explained the photoelectric effect using Planck’s quantum idea. -- only light at or above a threshold freq. will cause e– to be ejected from a metal surface ROYGBV e–e– – e– e– e– light source e– e– e– metal surface Frequency (i. e. , energy) of light determines IF e– are ejected or not, and with what KE. Intensity/brightness of light determines HOW MANY e– are ejected.

Einstein also expanded Planck’s idea, saying that energy exists only in quanta. Light has

Einstein also expanded Planck’s idea, saying that energy exists only in quanta. Light has both wavelike and particle-like qualities, and. . . so does matter. ?

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