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# Ch 4 Section 15-17

### Quantium numbers

Question | Answer |
---|---|

Werner Heisenberg | Uncertainty Principle: it is impossible to determine simultaneously the position and momentum of an e- Momentum is mass*velocity Detecting an e- requires use of electromagnetic radiation must speak of the electrons’ position about the atom in terms of |

Basic Postulates of Quantum Theory | Atoms and molecules can exist only in certain energy states. In each, the atom has a definite energy. When an atom or molecule changes its energy state, it must emit or absorb just enough energy to bring it to the new energy state (the quantum condition) |

Basic Postulates of Quantum Theory | Atoms or molecules emit or absorb radiation (light) as they change their energies. The frequency of the light emitted or absorbed is related to the energy change by a simple equation. |

Basic Postulates of Quantum Theory | Allowed energy states of atoms & molecules can be described by sets of quantum numbers. Four quantum numbers are necessary to describe energy states of electrons in atoms. |

Blocks | S, P, D, F |

quantium numbers | Quantum numbers play important roles in describing the energy levels of electrons and the shapes of the orbitals that describe distributions of electrons. An atomic orbital is a region of space in which the probability of finding an electron is high. |

Principal quantum number: n | Describes the main energy level (or shell); determines size of orbital (the bigger the n the bigger the orbital) n= 1, 2, 3, 4, 5, 6… |

Momentum quantum number: l | tells us the shape of the orbitals Within a shell (n number) different sublevels or subshells are possible l = 0, 1, 2, 3, 4, 5, .......(n-1) l = s, p, d, f, g, h, .......(n-1) |

Magnetic quantum number, ml | Designates a specific orbital within a subshell; determines the orientation of the orbitals within a subshell When l = 1 then p orbitals so have 3 px, py, pz, so ml can be -1, 0, 1 |

Spin quantum number, ms | Refers to the spin of the electron and the orientation of the magnetic field produced by the spin. ms = + ½ Each atomic orbital can accommodate no more than 2 e one with ms of + ½ and one with -1/2 |

The principal quantum number | has the symbol n. n = 1, 2, 3, 4, ...... “shells” The electron’s energy depends principally on n . |

The angular momentum quantum | number has the symbol l. l = 0, 1, 2, 3, 4, 5, .......(n-1) l= s, p, d, f, g, h, .......(n-1) tells us the shape of the orbitals. These orbitals are the volume around the atom that the electrons occupy 90-95% of the time. |

The symbol for the magnetic quantum number | is ml. 2l + 1 = # of ml ml = - l , (- l + 1), (- l +2), 0, (l -2), (l -1), l If l = 0 then there is one ml = 0. Tthere is only 1 value of ml.there is one s orbital per n value. n ml If l = 1 then ml = -1,0,+1. |

The last quantum number is the spin quantum number | The spin quantum number only has two possible values. ms = +1/2 or -1/2 Tells us the spin and orientation of the magnetic field of the electrons. Wolfgang Pauli discovered the Exclusion Principle: No 2 e- in an atom can have the same set of 4 quantum |

atomic orbital | a region of space in which the probability of finding an electron is high |