Presentation on theme: "Energy Levels and Orbitals"— Presentation transcript:
1Energy Levels and Orbitals An investigation into electrons and their location and behavior within the atomLearning Targets:Describe the process of excitation and emission of energy by an electron.Understand what each quantum number represents and how they are determined – energy level, subshell, orbital, and spin.
2Emission Spectroscopy The spectra that were shown through emission spectroscopy led Niels Bohr to question the structure of the atom.
3Emission Spectroscopy With white light, all of the colors of the visible spectrum are shown.
4Emission Spectroscopy Since that was NOT what the spectra of elements looked like, Bohr began to look at why only certain wavelengths of color appeared.
5Emission Spectroscopy E = hcλEnergy h = 6.63 x Js wavelengthc = speed of lightThis equation shows that larger wavelengths indicate lower amounts of energy and smaller wavelengths indicate higher amounts of energy... an inverse relationship.Bohr realized that the specific wavelengths revealed specific amounts of energy.
6Emission Spectroscopy Specific amounts of energy!!That inferred that energy within the atom existed at specific amounts. Bohr called these orbits, or energy levels.An electron cannot be in-between energy levels, it can only be within an energy level.Therefore, energy is quantized.The Bohr Model
7Emission Spectroscopy Bohr realized that the spectra were being created as electrons moved between these energy levels:If an electron absorbs energy, it may jump to a higher energy level.When an electron is at a higher energy level we say that the electron is in its “excited” state.When the electron releases energy in the form of radiation, we say that the electron has returned to its “ground” state.The type of radiation that is emitted depends on the amount of energy released.
8Emission Spectroscopy The Bohr ModelWhen energy enters the atom, an electron (shown in red) can absorb the energy becoming excited, AND jumping to higher energy levels.4th Energy Level1st Energy LevelEnergy Coming In!Nucleus3rd Energy Level2nd Energy Level
9Emission Spectroscopy The Bohr ModelWhen the electron releases the energy, the electron returns to lower energy levels. Other forms of electromagnetic radiation, besides visible light, can be emitted.4th Energy Level1st Energy LevelEnergy emitted (ultraviolet light)NucleusEnergy emitted (red light)Energy emitted (infrared)3rd Energy Level2nd Energy Level
10Emission Spectroscopy The Bohr ModelWhen the electron returns to its ground state, it has the option of jumping down multiple energy levels, rather than one at a time.4th Energy Level1st Energy LevelEnergy emitted (ultraviolet light)NucleusEnergy emitted (blue/green light)3rd Energy Level2nd Energy Level
11Emission Spectroscopy The Bohr ModelSince a sample of gas has many atoms, there are many electrons. This is why Bohr saw multiple colors.But there were other electromagnetic waves, too.4th Energy Level1st Energy LevelNucleusEnergy emitted (red light)Energy emitted (blue/green light)3rd Energy Level2nd Energy Level
12Emission Spectroscopy This is the full electromagnetic spectrum.
13Emission Spectroscopy Electromagnetic WavesBohr saw Visible Light:wavelength is in the range of 400 to 700 nanometers(4 x 10-7 meters)ROY G. BIVWhite light is made of all the colors of light
14Emission Spectroscopy Electromagnetic WavesGamma rays: cosmic radiation,very high energyUltraviolet rays (UV): solar radiation,high energyInfrared rays (IR): thermal radiation, remote controls, low energyMicrowave rays: microwave oven,very low energy
15Emission Spectroscopy Electrons release certain types of electromagnetic radiation as they fall to specific lower energy levels.Energy LevelChangeSpectra Emission2 --> 1 Ultraviolet3 --> 1 Ultraviolet4 --> 1 Ultraviolet3 --> 2 Visible Red4 --> 2 Visible Blue/Green5 --> 2 Visible Blue4 --> 3 Infrared
16Quantum Mechanical Model In addition to knowing that there were energy levels in the atom, three scientists began to notice other things...Heisenberg – impossible to know the exact position and exact speed of an electron at the same timeDe Broglie – electrons have wave-like properties, as in they move in wave patternsSchroedinger – developed probability of finding each electron in a given location
17Quantum Mechanical Model HeisenbergBohr suggested that the electrons move in perfect circles around the nucleus.Heisenberg showed that, instead, the electron moves in a three dimensional cloud of probability that is smeared out over the orbit – Heisenberg uncertainty principle
18Quantum Mechanical Model DeBroglieBohr suggested that the electrons move in perfect circles around the nucleus.DeBroglie showed that there were other shapes because the electrons moved like waves – wave-particle duality.
19Quantum Mechanical Model DeBroglieWatch this YouTube video.
20Quantum Mechanical Model SchrodingerSchroedinger realized how to put the theories of Bohr, Heisenberg, and DeBroglie together by creating a mathematical equation to find the most likely location for each electron within an atom – wave equation.Watch this YouTube video.
21Quantum Mechanical Model Every electron within an atom has “coordinates”. Schrodinger gave these coordinates numerical values, known as quantum numbers. Each quantum number describes part of the coordinates that determine the energy and probable location of any electron for any atom.
22Quantum Mechanical Model First Quantum Number Energy LevelEnergy levels begin at the number 1.Each level is higher in energy than the next.The higher in energy, the farther away from the nucleus.
23Quantum Mechanical Model Second Quantum Number SubshellAtoms are three dimensional.Within the energy levels exist different shapes, or subshells.The shapes are determined by how much energy is required to create them.
24Quantum Mechanical Model Second Quantum Number SubshellThere are four main shapes: s, p, d, and f.s – think spherep – think peanutd – think daisyf – think fireburst
26Quantum Mechanical Model Second Quantum Number SubshellSince the subshells are determined by how much energy is required to create them, lower energy levels have fewer subshells. (The lower the energy level, the lower the energy.)The 1st energy level can only contain the s subshell.A simple sphere does not take a lot of energy to create.
27Quantum Mechanical Model Second Quantum Number SubshellThe higher the energy level, the more subshells can be held.The 2nd energy level can contain the s and the p subshell.As Bohr suggested, these subshells are further away from the nucleus.
28Quantum Mechanical Model Second Quantum Number SubshellThe 3rd energy level must contain three subshells - the s, p, and d.In effect, the numeric value that represents the energy level also represents the number of subshells within that energy level.
29Quantum Mechanical Model To recap:Energy level 1 = 1 subshell (s)Energy level 2 = 2 subshells (s and p)Energy level 3 = 3 subshells (s, p, and d)Energy level 4 = 4 subshells (s, p, d, and f)etc.Why are more subshells present?Each energy level is larger than the previous. As a result, there are more possible locations for where an electron could reside.
30Quantum Mechanical Model Nucleus1s subshell2s subshell2p subshell3s subshell3p subshell
32Quantum Mechanical Model Watch this YouTube video.
33Quantum Mechanical Model Third Quantum Number OrbitalsDid you notice that there were different positions of some of the subshells?The different positions, or orientations, are called orbitals, not orbits.The orbitals are determined by which subshell they are in and in which positions they are.The s orbital does NOT have a different position.The p orbital has THREE different orientations – x, y, and z.
34Quantum Mechanical Model Third Quantum Number OrbitalsEach orbital has a specific number of locations on the x, y, z axes.- s has 1 orbital orientation (just s)- p has 3 orbital orientations (px, py, pz)- d has 5 orbital orientations (dxy, dxz, dyz, dz2, dx2-y2)- f has 7 orbital orientations (too complex to list)
35Quantum Mechanical Model Third Quantum Number OrbitalsIf the next subshell is called “g”, how many orbital orientations should it have?_________After “g” the next subshell would be “h”. How many orbital orientations should it have?911
36Third Quantum Number Orbitals There is 1 s orbitalThere are 3 p orbitalsThere are 5 d orbitalsThere are 7 f orbitals
37Quantum Mechanical Model Fourth Quantum Number Electron SpinEach electron can be spin up (+1/2) or spin down (-1/2)No two electrons in the same orbital orientation can have the same spin.With only one spin up and one spin down, the maximum number of electrons that can fit into any given orbital orientation is two.This is called the Pauli Exclusion Principle.
38Quantum Mechanical Model Let’s put it all together!
39Quantum Mechanical Model Energy LevelPossible SubshellsAtomic OrbitalsNumber of Electrons in Each SubshellMaximum Possible Electrons in Energy Level1s2p368d510184f71432