Chapter 4 Electron Configurations

1. Chapter 4 Electron Configurations

2. Pauli Exclusion Principle • No two electrons in an atom can have the same four quantum numbers.

3. Aufbau principle • An electron occupies the lowest-energy orbital that can receive it.

4. Hund’s Rule • Orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron, and all electrons in singly occupied orbitals must have the same spin

5. Principal Quantum Number Generally symbolized by n, it denotes the shell (energy level) in which the electron is located. • Number of electrons that can fit in a shell:2n2

6. Angular Momentum Quantum Number • The angular momentum quantum number, generally symbolized by l, denotes the orbital (subshell) in which the electron is located

7. Magnetic Quantum Number • The magnetic quantum number, generally symbolized by m, denotes the orientation of the electron’s orbital with respect to the three axes in space.

8. Spin Quantum Number • Spin quantum number denotes the behavior (direction of spin) of an electron within a magnetic field. • Possibilities for electron spin: +1/2 or – 1/2

9. Orbital filling table

10. Electron configuration of the elements of the first three series

11. Irregular confirmations of Cr and Cu Chromium steals a 4s electron to half fill its 3d sublevel Copper steals a 4s electron to FILL its 3d sublevel

12. 4.3 Electron Configuration • 3 rules for adding electrons to orbitals • Aufbau principle: an electron occupies the lowest-energy orbital hat can receive it • Pauli exclusion principle: no two electrons in the same atom can have the same set of four quantum numbers • Hund’s rule: orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron, and all electrons in singly occupied orbital must have the same spin

13. Representing electron configuration • The electron configuration for boron is 1s22s22p1 • How many electrons are present in an atom of boron? • What is the atomic number? • Write the orbital notation for boron  ___ ___ 1s 2s 2px 2py 2pz

14. Practice: write the electron configuration notation for nitrogen    1s 2s 2px 2py 2pz

15. Orbital Notation • Write the orbital notation for Carbon __ __ __ ___ ___ 1s 2s 2px 2py 2pz

16. Noble Gas Configuration • This is a short hand notation • [Ne]3s23p1 for the element Al

17. Homework • Read section 4.3 • Pg 116 section review #1-5 • Pg 118 # 18, 19, 20, 23, 24