1. Electronic Structure of Atoms Chapter 4 Electronic Structure of Atoms

2. Electronic Structure of Atoms Waves The distance between corresponding points on adjacent waves is the wavelength ( ).

3. Electronic Structure of Atoms Waves The number of waves passing a given point per unit of time is the frequency. For waves traveling at the same velocity, the longer the wavelength, the smaller the frequency.

4. Electronic Structure of Atoms Electromagnetic Radiation All electromagnetic radiation travels at the same velocity: the speed of light (c), 3.00 x 10 8 m/s. Only Frequency and Wavelength change.

5. Electronic Structure of Atoms The Nature of Energy The wave nature of light does not explain how an object can glow when its temperature increases. Max Planck explained it by assuming that energy comes in packets called quanta.

6. Electronic Structure of Atoms Quantum A quantum of energy is the minimum quantity of energy that can be lost or gained by an atom. Planck suggested that objects emit energy in small packets called quanta.

7. Electronic Structure of Atoms The Nature of Energy A photon is a particle of electromagnetic radiation having zero mass and carrying a quantum of energy

8. Electronic Structure of Atoms The Nature of Energy Another mystery involved the emission spectra observed from energy emitted by atoms and molecules.

9. Electronic Structure of Atoms Emission Spectrum The lowest energy state of an atom is its ground state. A state in which an atom has a higher potential energy than it has in its ground state is an excited state. When a narrow beam of light is shined through a prism, it is separated into 4 specific colors. The 4 bands are known as hydrogen’s line- emission spectrum.

10. Electronic Structure of Atoms Emission Spectrum When 1 st experimented with, scientists expected to get a continuous range of frequencies of electromagnetic radiation and not 4 frequencies. This was known as a continuous spectrum. Disproving the continuous spectrum led to an entirely new atomic theory known as quantum theory.

11. Electronic Structure of Atoms Quantum Theory Whenever an excited atom falls to its ground state or to a lower-energy excited state, it emits a photon of radiation. Excited neon atoms emit light when electrons in higher energy levels fall back to the ground state or lower levels. This is what produces the neon glow.

12. Electronic Structure of Atoms The Nature of Energy Niels Bohr adopted Planck’s assumption and explained these phenomena in this way: 1.Electrons in an atom can only occupy certain orbits (corresponding to certain energies).

13. Electronic Structure of Atoms The Nature of Energy 2.Electrons in permitted orbits have specific, “allowed” energies; these energies will not be radiated from the atom.

14. Electronic Structure of Atoms The Nature of Energy 3.Energy is only absorbed or emitted in such a way as to move an electron from one “allowed” energy state to another.

15. Electronic Structure of Atoms Quantum Numbers Electrons do not travel around the nucleus in neat orbits as Bohr thought but instead in certain regions called orbitals. An orbital is a 3-dimensional region around the nucleus that indicates the probable location of an electron. Orbitals have different shapes and sizes.

16. Electronic Structure of Atoms Value of l0123 Type of orbitalspdf

17. Electronic Structure of Atoms 1s = 2 electrons 2s = 2 electrons 2p = 6 electrons 3s = 2 electrons 3p = 6 electrons 3d = 10 electrons 4s = 2 electrons 4p = 6 electrons 4d = 10 electrons 4f = 14 electrons

18. Electronic Structure of Atoms Hund’s Rule

19. Electronic Structure of Atoms Orbital Diagrams Each box represents one orbital. Half-arrows represent the electrons. The direction of the arrow represents the spin of the electron.

20. Electronic Structure of Atoms

21. Electronic Structure of Atoms Lithium – atomic number 11 Draw the orbital notation

22. Electronic Structure of Atoms Boron’s electron configuration Atomic number = 5

23. Electronic Structure of Atoms The electron configuration of boron is 1s 2 2s 2 2p 1. How many electrons are present in an atom of boron? What is the atomic number for boron? Write the orbital notation for boron. The number of electrons is equal to the sum of the superscripts = ______ The number of protons = electrons so the atomic number = _____

24. Electronic Structure of Atoms Write both the complete electron configuration for iron, Fe.