Presentation on theme: "Pre-IB/Pre-AP CHEMISTRY"— Presentation transcript:
1 Pre-IB/Pre-AP CHEMISTRY Chapter 4 – Arrangement of Electrons in Atoms
2 Section 1 ObjectivesBe able to define: electromagnetic radiation, electromagnetic spectrum, wavelength, amplitude, frequency, photoelectric effect, quantum(pl. quanta), photon, ground state, excited state, line emission spectrum, continuous spectrum, energy level.
3 Section 1 ObjectivesBe able to explain the mathematical relationship between speed, wavelength, and frequency of a wave.Be able to describe what is meant by the wave-particle duality of light.Be able to discuss how the photoelectric effect and the line emission spectrum of hydrogen lead to the development of the atomic model.
4 Section 1 ObjectivesBe able to describe the Bohr model of the atom.
28 Light InteractionsWhite light is light consisting of all colorsof visible light. These colors are visible in a rainbow or through a prism.
29 VelocityThe velocity of a wave is a product of its frequency and wavelength.v= flv = velocityf = frequencyl = wavelength
30 VelocityThe velocity of light through a vacuum(c) is about 3.0 x 108 m/sec. It is slightly slower through matter.
31 Photoelectric EffectPhotoelectric effect refers to the emission of electrons from a metal when light shines on the metal.
32 Photoelectric EffectIt was found that light of a certain frequency would cause electrons to be emitted by a particular metal. Light below that frequency had no effect.
33 Emission SpectraIf an object becomes hot enough it will begin to emit light.
34 Emission SpectraMax Planck suggested that hot objects emit light in specific amounts called quanta (sing. quantum).
35 Equantum= hf Emission Spectra Planck showed the relationship between a quantum of energy and the frequency of the radiation.Equantum= hfEquantum= energy of a quantum in joulesh = Planck’s constantf = frequency
36 Wave-Particle Duality Einstein later said that light had a dual nature – it behaved as both a particle and a wave.
37 Wave-Particle Duality Each particle of light, Einstein said, carries a particular quantum of energy.
38 Wave-Particle Duality Einstein called the “particles” of light photons which had zero mass and carried a quantum of energy. The energy is described as:Ephoton= hf
39 Photoelectric EffectEinstein explained photoelectric effect by saying in order for an electron to be ejected from a metal, the photon striking it must have enough energy to eject it.
40 AttractionDifferent metals have stronger attraction for their electrons than other. Therefore, some must absorb more energy than others to emit electrons.
41 Ground StateThe lowest energy state of an atom is called its ground state.
42 Excited StateWhen a current is passed through a gas at low pressure, the atoms become “excited.”
43 Excited StateAtoms in an excited state have a higher potential energy than their ground state.
44 Excited StateAn “excited” atom will return to its ground state by releasing energy in the form of electromagnetic radiation.
45 Emission SpectraElements will emit radiation of certain frequencies. This reflects the energy states of its electrons and is called a bright-line or emission spectrum.
46 Emission SpectraThe emission spectrum of an element is like its “fingerprint”.SodiumHeliumMercury
47 Energy LevelsStudying the emission spectrum of hydrogen lead Niels Bohr to the idea of energy levels.
48 Energy LevelsThe spectrum Bohr and others observed was the result of excited electrons releasing photons as they returned to their ground states.
49 Energy LevelsThe difference in the energy of photons was reflected in the different frequencies of light they observed.
50 Section 2 ObjectivesBe able to define: diffraction, interference, Heisenberg Uncertainty Principle, Quantum Theory, quantum numbers, principal quantum number, angular momentum quantum number, magnetic quantum number, spin quantum number.Be able to distinguish between the Bohr model and the quantum model of the atom.
51 Section 2 ObjectivesBe able to explain how the Heisenberg Uncertainty Principle and the Schroedinger Wave Equation led to the idea of atomic orbitals.Be able to list the four quantum numbers that describe each electron in an atom.
52 Section 2 ObjectivesBe able to relate the number of sublevels corresponding to each of an atom’s main energy levels, the number of orbitals per sublevel, and the number of orbitals per main energy level.