08-Jun-2012

Knowledge Statements

1. Atomic theories have changed over time as new experimental evidence became available.
2. At the atomic molecular scale, the behavior of matter is described by quantum mechanics, where particles have both wave-like properties and particle-like properties.
3. Electromagnetic radiation (light) can be described as a wave, and as a particle.
4. The interaction of electromagnetic radiation and matter provides experimental evidence for the quantization of energy levels in atoms and molecules.
5. The uncertainty principle limits our ability to know everything about a particular atomic-molecular system. At the same time, it is possible to make very accurate predictions about the behavior of large numbers of particles.
6. The electrons in atoms are in distinct energy states that can be described by quantum numbers. No two electrons in an atom are in exactly the same set of energy state.
7. Electrons can be considered as “core” electrons, which are relatively strongly attracted to the nucleus and so do not take part in chemical processes, and valence electrons, which are less strongly attracted and can take part in chemical processes.
8. The periodic table can be understood on two levels:
   – It is organized to show the repeating macroscopic properties of elements
   – It is organized by the filling of electron energy levels (orbitals) – which is ultimately responsible for the
   element’s macroscopic properties.
   – Periodic Trends (ionization energies, atomic radii and electronegativities) are understood in terms of Coulombic interactions between electrons and between electrons and the nucleus, and quantum mechanical effects, which include electron orbital energies and distributions.

Performance expectations:

• Using evidence from experiments, explain how and why models of atomic structure changed over time.
• Construct diagrams, graphs and mathematical expressions to show the relationship between frequency, wavelength and velocity of a wave.
• Using a range of experimental evidence, explain (separately) why both light and electrons display both wave-like and particle-like properties.
• Explain, using absorption and emission spectra, how this evidence supports the idea that electrons have discrete energy levels within an atom, and why spectra can be used to identify elements wherever they occur in the universe.
• Gather data on a range of elements in the periodic table, construct graphical representations of the data, and use them to predict periodic properties such as atomic radius, ionization energies, and relative electronegativities of other elements.
• Explain the organization of the periodic table, based on repeating patterns of core and valence electrons.
• Represent, using the periodic table, the electron configurations of main group elements in periods 1–3.
• Represent, using noble gas notation, and in terms of core and valence electrons, electron configurations of main group elements in periods 1–3.
• Using the interactions between the nucleus and electrons, explain the trends in electronegativity, ionization energy, and atomic radius, both down a group and across a row in the periodic table.