大学化学课件CHAPTER8【荐】.pdf

Chapter 8 : Periodic properties of elements Text sections 8.1 – 8.9 Key Concepts Electronic configurations Periodic trends in atoms and ions Periodic trends in chemical behaviour The Periodic Law First proposed, independently, by Mendeleev and Meyer in 1869 : When elements are arranged in order of increasing atomic mass, certain sets of properties recur periodically . e m u l o V c i m o t A Atomic Number The Modern Periodic Table Mendeleev’s qualitative groupings can be understood using quantum mechanical models. Periodic table table Electron Spin : A Fourth Quantum Number Effect only seen for atoms with odd-numbers of electrons A spinning charge creates a magnetic field. Applying an external magnetic field causes a beam of atoms to split into different beams. Electron Spin : A Fourth Quantum Number - • Two possibilities for e spin, so define a quantum number, ms , that is either +1/2 or -1/2. Sometimes m is denoted with an s arrow (↑or ↓). • pair of e-’s with opposing spin has no net magnetic field. Atoms with odd number of e-s must have a net magnetic field. Electrons in atoms have four quantum numbers !! n : l : m : m l s Pauli Exclusion Principle: - • no two e s in an atom may have the same 4 quantum numbers • therefore no orbital may have more than 2 e- ’s, and they must have opposite spins • knowing the number orbitals (given by ml) in a sublevel allows us to determine the maximum # of e-s in th