2. Section 5-3 Section 5.3 Electron Configuration (cont.) electron configuration aufbau principle Pauli exclusion principle Hund's rule valence electrons electron-dot structure A set of three rules determines the arrangement in an atom.

3. Section 5-3 Ground-State Electron Configuration The arrangement of electrons in the atom is called the electron configuration.electron configuration The aufbau principle states that each electron occupies the lowest energy orbital available.aufbau principle

4. Section 5-3 Ground-State Electron Configuration (cont.)

5. Section 5-3 Ground-State Electron Configuration (cont.) The Pauli exclusion principle states that a maximum of two electrons can occupy a single orbital, but only if the electrons have opposite spins.Pauli exclusion principle Hund’s rule states that single electrons with the same spin must occupy each equal-energy orbital before additional electrons with opposite spins can occupy the same energy level orbitals.Hund’s rule

7. Section 5-3 Ground-State Electron Configuration (cont.)

8. Shorthand Configuration –Core e - : Go up one row and over to the Noble Gas. –Valence e - : On the next row, fill in the # of e - in each sublevel. –Example - Germanium [Ar]4s 2 4p 2 3d 10

9. Section 5-3 Ground-State Electron Configuration (cont.) Noble gas notation uses noble gas symbols in brackets to shorten inner electron configurations of other elements.

10. Full energy level (noble gases) Full sublevel (s, p, d, f) Half-full sublevel Stability

11. Electron Configuration Exceptions –Copper EXPECT :[Ar] 4s 2 3d 9 ACTUALLY :[Ar] 4s 1 3d 10 –Copper gains stability with a full d-sublevel. D. Stability

12. Electron Configuration Exceptions –Chromium EXPECT :[Ar] 4s 2 3d 4 ACTUALLY :[Ar] 4s 1 3d 5 –Chromium gains stability with a half-full d- sublevel. D. Stability

13. Section 5-3 Valence Electrons Valence electrons are defined as electrons in the atom’s outermost orbitals— those associated with the atom’s highest principal energy level.Valence electrons Electron-dot structure consists of the element’s symbol representing the nucleus, surrounded by dots representing the element’s valence electrons.Electron-dot structure

14. Section 5-3 Valence Electrons (cont.)

15. A.A B.B C.C D.D Section 5-3 Section 5.3 Assessment In the ground state, which orbital does an atom’s electrons occupy? A.the highest available B.the lowest available C.the n = 0 orbital D.the d suborbital

16. A.A B.B C.C D.D Section 5-3 Section 5.3 Assessment The outermost electrons of an atom are called what? A.suborbitals B.orbitals C.ground state electrons D.valence electrons