Pick up an Electrons Unit Packet How do the different energy levels relate to an electrons energy state?

Bohr Model: Lithium Why not draw all three electrons the same distance from the nucleus?

How did scientists figure out electron energy levels *How did scientists figure out electron energy levels? *Could they see them? Scientists got clues from light. Atoms absorb light and emit light in distinct ways.

PRISMS: What does a prism do? The prism breaks light into all of its separate colors by separating the wavelengths. If the light is sunlight, all the colors are present. This is called a continuous spectrum, because every color is present. All the colors flow together continuously. Every possible energy level of visible light is present.

A rainbow is another example of the continuous spectrum of sunlight..

You get a continuous spectrum from sunlight. But when scientists look at the light coming off just one element, hydrogen for instance, they don't see the whole rainbow. Instead they just get bright lines of certain colors. This is called a line spectrum because only certain lines of colors are present.

This is the line spectrum of neon. This is the line spectrum of hydrogen. This is the line spectrum of neon.

Absorption Spectrum atomic absorption spectra shows colors missing from the continuous spectrum (missing λ were absorbed by the element as the light passed through the sample).

Let look at all 3…. continuous absorption emission

In fact, every element has a unique line spectrum In fact, every element has a unique line spectrum. That’s how scientists figured out what stars are made of. They analyzed the light coming from the stars, and compared it to the spectra of known elements.

But why don’t elements emit a continuous spectrum like sunlight?

The color of a light corresponds to its energy.

Atoms are only emitting light of certain energies Atoms are only emitting light of certain energies. Why don’t they emit light of the other energies?

To explain this spectral line puzzle, Neils Bohr came up with a radical model of the atom which had electrons orbiting around a nucleus, but only in certain allowed energy levels.

Electrons can only be in certain energy levels Electrons can only be in certain energy levels. All other energy levels just are not possible. Electrons can "jump" between these special orbits, however, and when they jump, they either absorb or release energy.

It’s like climbing a ladder: You can stand on one rung or another rung, but not really between rungs. Electrons can be in one energy level or jump to another energy level, but They can’t be between energy levels.

Here’s how it’s not like a ladder: An electron moving between orbits disappears from one and reappears instantaneously in another without visiting the space between. This jump from one orbit to another is called the “quantum leap.”

Just like going up a ladder, it takes energy for an electron to move away from the positively charged nucleus. Remember, opposites attract. The electron “wants” to be near the nucleus. It takes energy to move a negative charge away from a positive charge.

Excited State: absorbs a photon (light) and makes a quantum leap to a higher energy level. - requires energy (light) to move away from nucleus Ground State: releases a photon (light) and makes a quantum leap to a lower energy level. - releases energy as light when electron moves toward nucleus

Let’s see how this works at http://www.colorado.edu/physics/2000/quantumzone/bohr.html http://www.cs.sbcc.edu/physics/solar/sciencesegment/bohratom.swf

The atoms you’ve been learning to draw are called Bohr models.

When you draw the electron rings, you’re drawing the energy levels that are allowed for the electrons.

Rings and Color The Visible light spectrum is know as ROYGBIV - Red, Orange, Yellow, Green, Blue, Indigo, Violet *Red having the least amount of energy and therefore being closest to the nucleus *Violet having the highest energy and therefore being the farthest from the nucleus. * All the other colors follow in order in between

Quantum of Energy e- are found on certain energy levels (orbitals) around the atom. maximum of seven energy levels in an atom. e- on the 1st energy level, closest to the nucleus, have the lowest energy. E- on the 7th energy level, farthest from the nucleus, have the highest energy. An e- requires one ‘quanta’ (minimum amount of energy gained or lost by an electron) of energy to jump to the next energy level.

Lets look at how the energy levels correlate to each ring!

HYDROGEN

Electromagnetic Spectrum EQ: What are the parts of the EM spectrum and how do wavelength, frequency, and energy correspond?

Electromagnetic Radiation A form of energy that exhibits wavelike behavior as it travels through space Different forms of electromagnetic radiation can be seen on the electromagnetic spectrum

Electromagnetic Spectrum Encompasses all forms of electromagnetic radiation, showing the differences of wavelength and frequency in the types of radiation. Organized from: Low energy High Energy Low Frequency  High Frequency Long Wavelength  Short Wavelength

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