LINKING THE ATOM TO THE ELECTROMAGNETIC SPECTRUM Electrons in the Atom 1 Chapter 4 - Section 1.

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LINKING THE ATOM TO THE ELECTROMAGNETIC SPECTRUM Electrons in the Atom 1 Chapter 4 - Section 1

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visible Light Use the spectroscope to look at the ceiling light and describe what you see. What kinds of waves might also be present? ____________________________________ ____________________________________ ____________________________________ ____________________________________ ____________________________________ ____________________________________ ____________________________________ 2 Chapter 4 - Section 1

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Frequency and Wavelength Wavelength (lambda) – length of a wave from one crest to another Frequency – How many times in one second the crest of a wave passes a particular point C = wavelength x frequency How are the frequency and wavelength related to the speed of light? ____________________________________ ____________________________________ ____________________________________ 4 Chapter 4 - Section 1

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Questions on The Electromagnetic Spectrum What’s the frequency of a radio wave? _____________________________________________________ What’s the wavelength of ultraviolet light? What’s its frequency? ____________________________________________________ Which has a higher frequency – an X-Ray or a radio wave? _____________________________________________________ What happens to the frequency as the wavelength increases? ______________________________________________________ 6 Chapter 4 - Section 1

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Complete the Following Electromagnetic Spectrum Ultraviolet to gamma Rays – Wavelength from _____________________ Frequency from ___________________ Visible light Wavelength Between above 10^2 nm to below 10^3 nm Infrared to Long Wave ____________________ And frequency from 7 Chapter 4 - Section 1

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu What can Light Do? When light shines on a metal an electron is ejected from a metal What are quanta? How do they interact with the electrons in the atom? ______________________________________________________ ______________________________________________________ Why can’t red light produce eject an electron from a metal and green light can? ______________________________________________________ What can we conclude from this? ______________________________________________________ _ Packets of energyPackets of energy Photoelectric effectsPhotoelectric effects 8 Chapter 4 - Section 1

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu What can Light Do? When light shines on a metal an electron is ejected from a metal 1. What are quanta? How do they interact with the electrons in the atom? Quanta (Quantum) are packets of energy. Light travels in packets of energy. If the packet or quantum is large enough, an electron can get excited (move to a higher energy level) or get ejected out of an atom of metal. When an electron is ejected it is called the photoelectric effect. 2. Why can’t red light produce eject an electron from a metal and green light can? The energy given off by red light is too weak to eject an electron but green light’s energy is strong enough to eject an electron from an atom. 3. What can we conclude from this? If we look at the electromagnetic spectrum, the lights with the higher frequencies have higher quanta and can eject electrons from the atom Packets of energy Photoelectric effectsPackets of energyPhotoelectric effects 9 Chapter 4 - Section 1

Light is Energy Energy of the photon E = hv h = Planck’s Constant = 6.626 X 10^-34 J*s v = frequency v= c/wavelength E = hc/wavelength What does the energy of the photon depend on?_________________________________________ Which is more energetic? Red light or Blue light?_________________________________________ 10 Chapter 4 - Section 1 Energy of a Photon

Light is Energy Energy of the photon E = hv h = Planck’s Constant = 6.626 X 10^-34 J*s v = frequency v= c/wavelength E = hc/wavelength 1.What does the energy of the photon depend on? The energy of the photon depends on the frequency and wavelength. The higher the frequency the higher the energy. 2.Which is more energetic? Red light or Blue light? Blue light is more energetic than red light because the frequency of blue light is higher than that of red light. 11 Chapter 4 - Section 1 Energy of a Photon

Photoelectric effect Light as particle and as wave 12 Chapter 4 - Section 1

How do the electrons behave in different elements? Let’s look at different lights filled with different elements and record the colors of light that we see. Compare the lights that you see for hydrogen with the ones you see for other lights. Look at the Hydrogen light and record the colors that you see through the 3D glasses or spectroscope. 1. Look at Helium and Nitrogen light and record colors seen. _________________________________- 2. What are they? How do you think it happens? ________________________________ ___________________________________ ___________________________________ Bohr’s Model of the atom 3. How do the electrons react to energy inputs? ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ 13 Chapter 4 - Section 1

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Answers to Questions 1. See your lab results for Hydrogen and Helium 2. The element emits specific lights in the visible range. These are the line emission spectrum. Energy is absorbed by the element and then released in the form of light 3. If the energy is strong enough, the electron will absorb the energy and move to a higher energy level and then release it in the form of light (see the next picture if unable to play video). Chapter 4 - Section 1 14

Photons and electrons What is the interaction between the electron and the photon in the absorption diagram? In the emission diagram? 15 Chapter 4 - Section 1

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Electrons and Electromagnetic Waves 1.What happens to hydrogen when electricity is passed through it? 2.How can we see the different lights that make up the pinkish light emitted? 3.What is the difference between ground state and excited state of an electron? 4.Define “ground state” and “excited state” of an atom. What happens when the excited atom returns to the ground state? 5.If hydrogen emits its own variation of colored light, What do you think happens when other elements have an electrical charge go through them or heat? 6.What’s a line-emission spectrum? 16 Chapter 4 - Section 1 HYDROGEN SPECTRUM

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Bohr’s Model of The Atom Electrons can circle the nucleus only in specific orbits or paths The atom has a definite, fixed energy in these “allowed paths” and the electron(s) is/are in their lowest energy level(s) The energy of the electron is higher when it is in orbits that are successively farther from the nucleus The electron can move to a higher energy level by gaining an amount of energy equal to the difference in energy between the initial and the higher energy orbit. When an atom is in its excited state, the electron is in a higher energy orbit. When the atom falls back from the excited state, the electron drops down to a lower-energy orbit and emits a photon that has an energy equal to the energy difference between the initial higher-energy orbit and the lower-energy orbit. See the absorption and emission illustration in slide 15. Chapter 4 - Section 1 17

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Answers to Questions Chapter 4 - Section 1 18 1.What happens to hydrogen when electricity is passed through it? _The electron in Hydrogen absorbs the energy and moves to a higher energy level. It then releases it in the form of specified colors of light; creating the emission line spectrum 2.How can we see the different lights that make up the pinkish light emitted? We can use a prism or 3_-D glasses which act like prisms. 3.What is the difference between ground state and excited state of an atom? The ground state is when the electrons in the atom are in their normal energy level and the excited state is when the atom moves to a higher energy level. When the excited atom returns to its normal state or normal energy level, it electrons return to their nomal energy levels and release energy in the form of a photon. 4.Define “ground state” and “excited state” of an atom. What happens when the excited atom returns to the ground state? See question 3. The electron in the atom releases energy in the form of EM rays and it goes back to its normal energy level. 5.If hydrogen emits its own variation of colored light, What do you think happens when other elements have an electrical charge go through them or heat? They emit their own line emission spectrum 6.What’s a line-emission spectrum? It is the particular series of lights emitted by an atom when the electrons of that atom are in a higher energy level than normal and then return to their normal energy.

What other elements can we test? Read the instruction. What are the elements that we will be testing? Follow instruction for flame test And record results on the chart in the next page. 19 Chapter 4 - Section 1

Results of Flame Test How do you think this property can be used? 20 Chapter 4 - Section 1

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Exit Ticket Return this page to Mrs. McKinley before leaving Write 3 things that you have learned today 1. _________________________________ 2. ________________________________ 3. _______________________________ How is the electromagnetic spectrum related to the electrons in the atom? ___________________________________________________ ___________________________________________________ ==================================== 21 Chapter 4 - Section 1