1. Mullis Chemistry Holt Ch.41 Arrangement of Electrons in Atoms Principles of electromagnetic radiation led to Bohr’s model of the atom. Electron location is described using identification numbers called quantum numbers. Rules for expressing electron location results in a unique electron configuration for each element.

2. Mullis Chemistry Holt Ch.42 Building electron configurations for the ground state of an atom Aufbau: Lowest energy level 1st Pauli Exclusion: Only 2 e- per orbital, opposite spin Hund: One electron per orbital until that level is full (same spin) Theater analogy: 1. Enter at front. Climb stairs and sit in first empty section you reach. 2. Each bench seats 2 people. One male and one female per bench. 3. Within a level, ladies first. One lady per bench until each bench is occupied, then one man per bench to fill that level.

3. Mullis Chemistry Holt Ch.43 Example: Building electron configurations for the ground state of an atom Phosphorous: 15 electrons: Start with 1s. Each s can hold 2 electrons. Each p can hold 6 electrons. Place one electron per orbital, then pair until that level is full. Only then go to the next level.

4. Mullis Chemistry Holt Ch.44 Wave Description of Light Electromagnetic radiation is a form of energy that exhibits wavelike behavior as it travels through space Wavelength (λ) –Distance between corresponding points on adjacent waves. –Unit: nm,cm,m Frequency (ν) –Number of waves that pass a specific point in a given time –Unit: Hz or waves/sec Recall that Speed = Distance/time (m/sec) Speed of light (c) C = λ ν

5. Mullis Chemistry Holt Ch.45 Behavior of Light Photoelectric effect –The emission of electrons when light shines on the metal –Scientists found that below a certain frequency, no electrons were emitted. –Light also behaves as a particle: Since hot objects do not emit em energy continuously, they must emit energy in small chunks called quanta. Quantum –Minimum quantity of energy that can be gained or lost by an atom

6. Mullis Chemistry Holt Ch.46 Light as a particle and a wave Planck and Einstein Max Planck: Relationship between quantum of energy and wave frequency Planck’s constant h = 6.626 x 10 -34 J-s E = hνE is energy, ν is frequency Albert Einstein: Established dual wave-particle nature of light 1 st –Einstein explained PE effect by proposing that EM radiation is absorbed by matter only in whole numbers of photons. –Electron is knocked off metal surface only if struck by one photon with certain minimum energy.

7. Mullis Chemistry Holt Ch.47 Quantum Theory Ground state: An atom’s lowest energy state Excited state: Higher potential energy than ground state. Photon: A particle of electromagnetic radiation having zero mass and carrying a quantum of energy (i.e., packet of light) Only certain wavelengths of light are emitted by hydrogen atoms when electric current is passed through—Why?

8. Mullis Chemistry Holt Ch.48 Niels Bohr links hydrogen’s electron with photon emission Bohr proposed that an electron circles the nucleus in allowed orbits at specific energy levels. –Lowest energy is close to nucleus Bohr’s theory explained the spectral lines seen in hydrogen’s line emission spectrum, but it did not hold true for other elements.

9. Mullis Chemistry Holt Ch.49 Quantum Numbers Principal quantum number Angular momentum quantum number Magnetic quantum number Spin quantum number

10. Mullis Chemistry Holt Ch.410 Quantum numbers 1s ____ 2s ____2p ____ ____ ____ 3s _____ Principal quantum number Magnetic quantum number Angular momentum quantum number

11. Mullis Chemistry Holt Ch.411 Magnetic quantum number Magnetic quantum number is the orientation of an orbital around the nucleus. It is the number of orbitals in a sublevel. The s sublevel has 1 orbital. The p sublevel has 3 orbitals. The d sublevel has 5 orbitals. The f sublevel has 7 orbitals. Orbitals per sublevel s1 p3 d5 f7

12. Mullis Chemistry Holt Ch.412 Atomic Structure Summary of Contributions Max Planck –A hot object emits energy in small, specific amounts called quanta. Albert Einstein –E = mc 2 –Light behaves as both a wave and a particle. –Each particle of light carries a photon ( a quantum of energy). Niels Bohr –Created a model of the atom that showed a single electron of hydrogen orbits the nucleus only in allowed orbits with a fixed energy.

13. Mullis Chemistry Holt Ch.413 Atomic Structure Summary of Contributions, continued Werner Heisenberg –Uncertainty principle: It is impossible to determine simultaneously both the position and velocity of an electron. Erwin Schrödinger –Helped lay the foundation for quantum theory with an equation that treats electrons like waves.

14. Mullis Chemistry Holt Ch.414 Electron Configuration: The Rules Aufbau principle –An electron occupies the lowest energy orbital that will receive it. Pauli exclusion principle –No two electrons in the same atom can have the same set of 4 quantum numbers. –Therefore, electrons can pair in an orbital as long as their spins are opposite. Hund’s rule –Each of the orbitals at a particular level have one electron before any of them can have two electrons. –All single electrons in the orbitals at a particular level have the same spin.