Electrons in Atoms Bohr Model Chapter 3 Electrons in Atoms Bohr Model

Bohr’s Model Nucleus Electron Orbit hyperlink Energy Levels

Student check for understanding Bohr’s Model Evaluate the Bohr model on its positive merits and its negative merits

Student check Bohr’s Model Why don’t the electrons fall into the nucleus?

Student check Bohr’s Model Why don’t the electrons fall into the nucleus? Forces: Gravitational Centrifugal outward force Centripetal force

} Bohr’s Model Further away from the nucleus means more energy. Fifth There is no “in between” energy Energy Levels Fifth Fourth Third Increasing energy Second Hyper link First Nucleus

The Quantum Mechanical Model Energy is quantized. It comes in chunks. A quanta is the amount of energy needed to move from one energy level to another. Since the energy of an atom is never “in between” there must be a quantum leap in energy.

Atomic Orbitals Principal Quantum Number (n) = the energy level of the electron. These are called atomic orbitals Regions where there is a high probability of finding an electron.

Light The study of light led to the development of the quantum mechanical model. Light is a kind of electromagnetic radiation. Electromagnetic radiation includes many kinds of waves All move at 3.00 x 108 m/s ( c)

Parts of a wave Crest Wavelength Amplitude Origin Trough

Frequency The number of waves that pass a given point per second. Units are cycles/sec or hertz (hz) Abbreviated n the Greek letter nu c = ln

Frequency and wavelength Are inversely related As one goes up the other goes down. Different frequencies of light is different colors of light. There is a wide variety of frequencies The whole range is called a spectrum

Low energy High energy Radiowaves Microwaves Infrared . Ultra-violet X-Rays GammaRays Low Frequency High Frequency Long Wavelength Short Wavelength hyperlink Visible Light

Student Check Inversely related? If radio waves have a low frequency what happens to their wavelength? If gamma rays have a short wavelength what happens to their frequency

How color tells us about atoms Atomic Spectrum How color tells us about atoms

Prism White light is made up of all the colors of the visible spectrum. Passing it through a prism separates it. hyperlink

If the light is not white By heating a gas with electricity we can get it to give off colors. Passing this light through a prism does something different.

Atomic Spectrum Each element gives off its own characteristic colors. Can be used to identify the atom. How we know what stars are made of.

These are called discontinuous spectra Or line spectra unique to each element. These are emission spectra The light is emitted given off. hyperlinks

Spectrum and the stars How can you use the spectrum to determine what the sun is made of. What other information can be determined look at the emission spectrum Hyper link Temp/speed/ age

Light is a Particle Energy is quantized. Light is energy Light must be quantized These smallest pieces of light are called photons. Energy and frequency are directly related.

After Before Photon changes wavelength Photon Electron Changes velocity Moving Electron

Student check Summarize how Light is produced using the Bohr model

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