Quantum Number | Quantum Name | Values |

n | shell |
1, 2, 3, 4, ... (infinity) |

l | subshell | 0, 1, 2, ... (n - 1) |

m_{l} | orbital | -l ... 0 ... +l |

m_{s} | electron spin | +1/2 or -1/2 |

Each electron in an atom can have its own unique "address" or set of four quantum numbers.

*Example:* Consider a **Beryllium** atom with four electrons. Beryllium is in the second period, so possible n values are 1 and 2. Electrons are filled using the lowest value of n (or n + l), so the electrons will be placed into the n=1 shell before they enter the n=2 shell.

__When n = 1__, the only allowed value of l is 0; likewise, the only allowed value of m_{l} = 0. We will place the first two electrons in a 1s orbital. Each electron can have either a "spin up" (m_{s} = +1/2) or "spin down" (m_{s} = -1/2) configuration.

__When n = 2__, allowed values of l are 0 and 1. Lowest (n + l) values are filled first; hence, a (n + l) value of (2 +0) = 2 will be filled before a (n + l) value of (2 + 1) = 3. When l = 0, the only allowed value of m_{l} = 0. We will place the next two electrons in a 2s orbital. Each electron can have either a "spin up" (m_{s} = +1/2) or "spin down" (m_{s} = -1/2) configuration.

The** nl^{x} notation** is used to describe the subshell and/or orbital in which the electrons are assigned in an atom or ion. The electron filling order is found by using the

Value of l | Letter | Notes |

0 | s | Stupid |

1 | p | People |

2 | d | Drink |

3 | f | Freakin' |

4 | g | Gasoline |

*Example:* Considering **Beryllium** again, we would place the first two electrons in the 1s subshell (**n + l** = 1 + 0 = **1**), and the second two electrons in the 2s subshell (**n + l** = 2 + 0 = **2**, so 2s is filled after 1s due to a lower (n + l) value.) The* complete electron configuration* for neutral Beryllium with its four electrons in the ground state would be:

*Example:* Considering **Aluminum** with its 13 electrons in the neutral ground state, we would place the electrons in successively higher subshells using the (n + l) values (or by consulting an Aufbau diagram.) The *complete electron configuration* for neutral Aluminum with its 13 electrons in the ground state would be:

2. When l = 2, possible values of m

3. When m

4. Is 3d a correct combination of n and l quantum numbers?

5. Is 2f a correct combination of n and l quantum numbers?

6. The values of n and l in a 5p subshell are:

7. The correct electron configuration for carbon

8. What neutral element has the following electron configuration: 1s

9. What neutral element has the following electron configuration: 1s

10. What neutral element has the following electron configuration: 1s