Download Topic 7. 1 Atomic Structure

Name ___________________ Date _______________ Block ________
Topic 7. 1 Atomic Structure
7.1.1 Describe a model of the atom that features a small nucleus surrounded by electrons.
 The modern atom has gone through a few stages of development
1) _____________’s Atomic Theory – idea of an atom
2) JJ Thompson – 1890 – negative charge (________________)
3) Earnest Rutherford – 1911 - positive nucleus (protons)
4) Niels ___________ – 1913 – orbital shells
5) Chadwick – 1932 – neutrons
 This is a VERY simplified idea of the atom
 Nucleus
 Protons – positive charge – _______________
 Neutrons – no charge
 Diameter order of 10-15m
 Electron “____________”
 Electrons – negative charge – 1.6 x 10-19C
 Diameter order of 10-10m
 The nucleus is about 100,000 times smaller than the electron orbits.
 Imagine a _______ in the center of a football field with the track being the orbits.
 Protons and Neutrons have very similar mass.
 Protons and Neutrons are about ________ times bigger than electrons.
Actual Values are: Proton –
Neutron -
Electron -
7.1.2 Outline the evidence that supports a nuclear model of the atom
 Dalton’s Atomic Theory
1) All matter is composed of extremely small particles called atoms.
2) All atoms of a given element are _____________.
3) Atoms cannot be created, _______________ into smaller particles, or destroyed. (This part
proven wrong)
4) Different atoms combine in simple whole number ratios to form compounds.
5) In a chemical reaction, atoms are separated, combined or rearranged.
Subatomic Particles and the Atom
 J. J. _______________ – 1890-1900
 Used ________________ tube to prove existence of electron.
 Proposed “Plum Pudding Model”
 Cathode ray tube
 Stream of charged particles (electrons). *** see video***
 Plum Pudding - ______
 Ernest Rutherford
 _____________________ experiment
 Used to prove the existence of a positively charged core (________________)
 Fired alpha particles(2protons and 2 neutrons) into very thin gold foil.
 The results were “like firing a large artillery shell at a sheet of paper and having the shell come back and
hit you!”
 What should have happened?......
 What did happen?........
 After performing hundreds of tests and calculations, Rutherford was able to show that the diameter of
the nucleus is about 105 times smaller than the diameter of the atom
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 Subatomic Particles and the Atom
 James __________________ – 1932
 Worked with Rutherford.
 Noted there was _____________ in the nucleus, but wasn’t the protons.
 Concluded that neutral particles must also exist in nucleus.
 Bombarded a beryllium target with alpha particles
 _____________ particles are helium nucleus
 Discovered that, carbon was produced with another particle.
 **** Write reaction on board****
 Concluded this particle had almost identical mass to proton but no charge.
 Called it a _______________
 Three main particles:
 Proton
 Positive
 In nucleus
 Neutrons
 Neutral
 In nucleus
 Electrons
 Negative
 Orbiting the nucleus (not inside)
7.1.3 Outline one limitation of the simple model
of the nuclear atom.
7.1.4 Outline evidence for the existence of atomic
energy levels.
Collapse
 If Rutherford’s was correct, electrons orbiting
would undergo centripetal _________________.
 This would mean they would radiate
electromagnetic waves.
 Meaning they would loose energy
 Meaning the atom would collapse on it’s self
Glowing Gas
 If low-pressure gases are heated or current is passed through them they glow.
 Different ____________ correspond to their wavelengths.
 Visible spectrum _______(violet) to 750nm(red)
 Diagram:
 When single element gases such as hydrogen and helium are excited only specific wave lengths were
emitted.
 These are called ______________line spectra
 If white light is pass through the gas the emerging light will show dark bands called absorption lines.
 They correspond to the emission lines.
 ***Draw diagram***
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LIMITATION
 Rutherford’s model didn’t explain why atoms emitted or absorbed
only light at ______________ wavelengths.
 1885 JJ Balmer showed that hydrogen’s four emission lines fit a
__________________ formula.
 This “Balmer series” also show the pattern continued into nonvisible ultra-violet and infra-red.
 Bohr called these “______________________”
 Reasoned that the electrons do not lose energy continuously but
instead, lose energy in discrete amounts called “____________”.
 He agreed with Rutherford that electrons orbit the nucleus but only
certain orbits were allowed.
 The _________________ force between protons and electrons
holds electrons in orbit
 Electron never found between these levels. (“jumps” instantly)
 Only radiates energy when it “jumps” down.
 _______________ energy when it “jumps” up.
 Total energy stays constant
 Bohr explained the emission and absorption line spectra with the idea that electrons absorbed only certain
quantity of energy that allowed it to move to a higher orbit or energy level.
 Each element has its own “____________________”.
Energy Level Diagram
 Ground state – ____________ energy level – smallest possible radius
 Excited state – when an electron __________ energy and jumps to a higher energy level.
 Once an electron jumps back to a lower state it gives off energy in the form of a photon.
 These phot s are the emission spectrum.
 The amount jumped correlates to the energy of the photon.
 Greater the jump means the greater the energy is emitted.
 Each jump corresponds to a different amount of energy being released. This means we can calculate the
frequency and wavelength of light that will be
produced.
Energy of a light quantum
 E = hf
 E = energy of a quantum
 h = Planck’s constant (6.63 x 10-34Js)
 f = frequency
Sample Problem C
 An electron in a hydrogen atom drops from
energy level E4 to energy level E2. What
frequency of the emitted photon, and which
line line in the emission spectrum corresponds
to this event?
 First find the amount of energy lost
 Elost = E4 – E2
 Elost = (-0.85eV) – (-3.40eV)
 Elost = 2.55 eV
 Second, convert eV into J.
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 1eV = 1.6 x 10-19J
 Answer: 4.08 x 10-19J
 Third use Planck’s equations to find the
frequency.
 E = hf
 f = 6.15 x 1014 Hz
 Fourth decide which line corresponds to this
even.
 Answer: Green light
 v=fλ
Your practice
 Practice C, pg 769 in book, #2 – 4
7.1.5 Explain the terms nuclide, isotope and
nucleon
7.1.6 Define nucleon number A, proton
number Z, and neutron number N.
 Isotopes
 More evidence for neutrons is the existence of isotopes.
 When nuclei of the same element have different numbers of ______________ .
 Carbon has 6 isotopes: Carbon-11, Carbon-12, Carbon-13, Carbon-14, Carbon-15, Carbon-16.
 All have 6 protons but each has different number of neutrons.
 The different isotopes don’t exist in nature in ____________ amounts.
 Carbon:
 C – 12 is most abundant (___________)
 C – 13 is next (__________)
 This is where atomic mass comes from. It’s the weighted average mass of all the different isotopes.
 Nuclei of different atoms are known as nuclides.
 Ex. C – 12, C – 14
 Both are carbon but different isotopes
 Their nuclei have different numbers of neutrons.
 These are different nuclides.
7.1.7 Describe the interactions in a nucleus
 How do like charge (protons), stay stuck together?
 We already know that like charges repel each other.
 We have also seen that they are stronger than gravitational forces.
 ____________ Force – The force that binds the nucleus together.
 It is an attractive force that acts between all nucleons.
 _____________– range interactions only (up to 10-15m)
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Answers: 1) 4.56 x 10 14Hz, line 4
3) 1.61 x 1015Hz
2) 2.73 x 1014Hz, infrared
4) 10
5) E6 to E2; line 1
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7.3.3 - Define the term unified atomic mass unit.
7.3.4 - Apply the Einstein mass-energy equivalence relationship.
7.3.5 - Define the concepts of mass defect, binding energy and binding energy per nucleon.
7.3.7 - Solve problems involving mass defect and binding energy.
 Unified Mass Unit
 Because the mass of an atom is so small a new unit was created.
 Some times called “_________________”
 1 u = 1.66053886 x 10-27 kg
 ___________ = one atom of carbon-12
 Resting Energy
 Mass of a nucleus is sometimes expressed in terms of ________________.
 A particle has a certain amount of energy associated with its mass.
 Relationship between rest energy and mass:
 _________________
 Conservation of mass
 It doesn’t always happen with nuclear processes.
 Some times mass is converted or ________ in the form of energy.
 1u = 931.49 MeV
 So that means that one proton IS ________________ of energy.
 Mass is energy, energy is mass THEY ARE THE SAME THING!!! AHHHHHH!!!!!!
 Nuclear Stability
 What happens when you place two negative charged particles next to each other?
 What happens when you place two positively charged particles next to each other?
 So why doesn’t a nucleus explode?
 It shouldn’t stay together.
 ______________
 Attractive force
 Independent of electric charge
 Very short range
 ________________
 Spread the protons apart to help balance electrical repulsion and strong attraction
 Binding Energy
 Particles in a stable nuclease need an ___________t of energy to break the strong nuclear force.
 When to unbound particles come together energy is released. (think nuclear reactions)
 Turns out these quantities of energy are the same.
 Called the _________________
 Binding energy is the energy it takes to hold the atom together.
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 Think of it this way….
 Recall that mass is energy.
 Carbon – 12
 Atom of carbon – ______________, less rest energy
 Constituent parts of – heavier, more rest energy
 What happen to that little bit of matter?
 It is used as the _______________ to bind together the atom.
 The difference in the two masses is known as mass defect (∆m)
 Put it all together
 Binding energy = mass defect x (speed of light)2
 Ebind = ∆m c2
 E = mc2
Example
 The nucleus of the deuterium atom, called deuteron, consists of a proton and a neutron. Given that the
atomic mass of deuterium is 2.014 102u, calculate the deuteron’s binding energy in MeV.
 Answer: 2.224MeV
Together
 If the phosphorus has a mass of 30.973 762u, then what is the binding energy that holds the nucleus together
in MeV?
 Answer:
 Practice A, pg 795 in book, #1,3-4
 Answers:
1) 160.65MeV, 342.05MeV
2) 0.764MeV
3) 7.933MeV
4) 7.5701 MeV/nucleon
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