Models of the Atom In science a wrong

Flaws in the Bohr model Increasing energy of orbits n=3 e- n=2 e- e-

Models of the Atom So far theories amounted to. . . e + e

$The problem was… If we pass light WAVES through a diffraction grating, we obtain$

$ELECTRONS were believed to be PARTICLES. Passing electron particles through a diffraction grating produces$

Electrons as Waves Evidence: DIFFRACTION PATTERNS VISIBLE LIGHT ELECTRONS

Models of the Atom Until then theories had amounted to. . . e +

The wavelike properties of electrons led to the charge cloud model Charge-cloud model (present)

DE BROGLIE WAVELENGTH Prince Louis de Broglie - 1932 De Broglie discovered that all

Erwin Schrödinger (1926) Quantum mechanics • electrons can only exist in specified energy states

Quantum Mechanics • Heisenberg Uncertainty Principle – Impossible to know both the velocity and

Erwin Schrödinger (1926) Electron Cloud Model (orbital) dots represent probability of finding an e

Quantum Mechanical Model Niels Bohr & Albert Einstein Modern atomic theory describes the electronic

Current View • The atom is mostly empty space • Two regions – Nucleus

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Models of the Atom "In science, a wrong theory can be valuable and better than no theory at all. " Sir William L. Bragg

Flaws in the Bohr model Increasing energy of orbits n=3 e- n=2 e- e- n=1 ee- e- e- A photon is emitted with energy E = hf The Bohr model of the atom, like many ideas in the history of science, was at first prompted by and later partially disproved by experimentation.

Models of the Atom So far theories amounted to. . . e + e +e +e e + e Dalton’s Greek model (400 (1803) B. C. ) Thomson’s plum-pudding model (1897) - - - + Rutherford’s model (1909) Bohr’s model (1913)

$The problem was… If we pass light WAVES through a diffraction grating, we obtain$

The problem was… If we pass light WAVES through a diffraction grating, we obtain a diffraction pattern VISIBLE LIGHT

$ELECTRONS were believed to be PARTICLES. Passing electron particles through a diffraction grating produces$

ELECTRONS were believed to be PARTICLES. Passing electron particles through a diffraction grating produces a diffraction pattern ELECTRONS

Electrons as Waves Evidence: DIFFRACTION PATTERNS VISIBLE LIGHT ELECTRONS

Models of the Atom Until then theories had amounted to. . . e + e +e +e e + e Dalton’s Greek model (400 (1803) B. C. ) Thomson’s plum-pudding model (1897) - - - + Rutherford’s model (1909) Bohr’s model (1913)

The wavelike properties of electrons led to the charge cloud model Charge-cloud model (present)

Wave – particle duality

DE BROGLIE WAVELENGTH Prince Louis de Broglie - 1932 De Broglie discovered that all particles with momentum have an associated wavelength.

Erwin Schrödinger (1926) Quantum mechanics • electrons can only exist in specified energy states Electron cloud model • orbital: region around the nucleus where e- are likely to be found

Quantum Mechanics • Heisenberg Uncertainty Principle – Impossible to know both the velocity and position of an electron at the same time g Microscope Electron Werner Heisenberg ~1926

Erwin Schrödinger (1926) Electron Cloud Model (orbital) dots represent probability of finding an e -

Quantum Mechanical Model Niels Bohr & Albert Einstein Modern atomic theory describes the electronic structure of the atom as the probability of finding electrons within certain regions of space (orbitals).

Current View • The atom is mostly empty space • Two regions – Nucleus • protons and neutrons – Electron cloud • region where you might find an electron