Chapter 5 Electrons in Atoms

I. The Dual Nature of Matter A. Matter and energy are related are related 2 E=mc E=mc B. As matter gets smaller it behaves more like energy "As far as the laws of mathematics refer to reality, they are not certain; as far as they are certain, they do not refer to reality."--Albert Einstein "As far as the laws of mathematics refer to reality, they are not certain; as far as they are certain, they do not refer to reality."--Albert Einstein

C. Scientists in the early 1900’s observed that elements emitted unique frequencies of visible light when heated with a flame C. Scientists in the early 1900’s observed that elements emitted unique frequencies of visible light when heated with a flame

D. Electromagnetic radiation – form of energy that exhibits wavelike behavior Visible light is a type of electromagnetic radiation Visible light is a type of electromagnetic radiation To understand how small amounts of matter ( like electrons) behave we must study wave properties To understand how small amounts of matter ( like electrons) behave we must study wave properties

II. The Wave Nature of Light

The Electromagnetic Spectrum <> <> <>

II. Wave Nature of Light

The wavelength, the frequency, and the speed of light obey the following relationship: The wavelength, the frequency, and the speed of light obey the following relationship: wavelength * frequency = speed of light. wavelength * frequency = speed of light. The speed of light is usually represented by c, the wavelength by the lower case Greek letter lambda, l and the frequency by lower case Greek letter nu n. In these symbols, the above formula is: The speed of light is usually represented by c, the wavelength by the lower case Greek letter lambda, l and the frequency by lower case Greek letter nu n. In these symbols, the above formula is: l n = c l n = c

Max Plank In his research on the radiation from a hot (black) body, Max. Plank made a simple proposal. In his research on the radiation from a hot (black) body, Max. Plank made a simple proposal. He suggested that light consists of photons. He suggested that light consists of photons.

The energy, E, of each individual photon of a monochromatic light wave, is proportional to the frequency, n, of the light: The energy, E, of each individual photon of a monochromatic light wave, is proportional to the frequency, n, of the light: E = h n E = h n where h (= 6.626*10-34 J s) is now known as the Planck constant. Often, we write h = 6.626e-34 J s for simplicity. where h (= 6.626*10-34 J s) is now known as the Planck constant. Often, we write h = 6.626e-34 J s for simplicity.

deBroglie Proposal Appealing to symmetry of nature, deBroglie proposed that electrons, too, have a wave nature and a wavelength! Appealing to symmetry of nature, deBroglie proposed that electrons, too, have a wave nature and a wavelength! In particular, deBroglie proposed that the wavelength of a body could be found from

Flame Test Lab Questions Put the unknowns in order from high to low energy. Put the unknowns in order from high to low energy. Explain why the order makes sense according to what you know about wavelength. Explain why the order makes sense according to what you know about wavelength. Why do the different elements in the lab emit different frequencies of light. Why do the different elements in the lab emit different frequencies of light.

Electron Configuration Notation Aufbau principle – electrons occupy the lowest energy orbital possible Aufbau principle – electrons occupy the lowest energy orbital possible Pauli exclusion principle – if two electrons occupy the same orbital they must have opposite spins (no two electrons can have the exact 4 same quantum numbers) Pauli exclusion principle – if two electrons occupy the same orbital they must have opposite spins (no two electrons can have the exact 4 same quantum numbers) Hundz rule – electrons occupy orbital within a sub-shell singly until they have to pair Hundz rule – electrons occupy orbital within a sub-shell singly until they have to pair