Name 5.3 Electron Configurations Date Hour Ground State Electron Configurations  Low energy systems are ______________________ than high energy systems o Electrons will arrange to have the __________ possible energy o Lowest‐energy arrangement is called the element’s _______________________ Principle Quantum Number (n) Orbital # of # of Name Orbitals electrons • Indicates the relative ________ and ___________ of atomic orbitals. • As n increases, the electron spends more time ___________________________________. Three Rules Defining Electron Arrangement • The Aufbau Principle: each electron occupies the lowest energy orbital available o All orbitals related to an energy sublevel are of __________________ energy. o In a multi‐electron atom, the energy sublevels within a principal energy level have ________________________energies.  _______ orbitals have more energy than _______ o In order of increasing energy, the sequence of energy sublevels within a principal energy level is s, p, d, and f. o Orbitals from different principal energy levels can ‘overlap.’  4s has _______________ energy than 3s •
The Pauli Exclusion Principle states that a maximum of ______ electrons may occupy a single atomic orbital, but only if the electrons have __________________ ____________. 2p
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Hund’s Rule states that electrons _____________ occupy each equal energy orbital before _______________ ______. 2p
Electron Configurations: • Sulfur • Potassium • Carbon • Iron Orbital Diagrams and Electron Configuration • Orbital Diagram includes a box for each of the atom’s orbitals (2 electrons) o Each box is labeled with the principal quantum number and sublevel o Empty box = unoccupied orbital o Box with 1 up arrow = orbital with 1 electron o Box with both an up and a down arrow = filled orbital • Example: Ground‐State Carbon Atom # Electrons = 1s
2s
2p
• Example: Ground‐State Fluorine Atom # Electrons = 1s
2s
2p
• Electron Configuration Notation designates principal energy level, sublevel, and number of electrons in each orbital. 
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Electron Configuration for Helium: 1s2 o Read “One S Two” o Principal quantum number = 1 o Sublevel = s o # of Electrons = 2 Example: Sodium Number of electrons = ______ Note: The number of electrons will equal the sum of the exponents 1s
2s
2p
3s
PRACTICE: Write the ground state electron configuration for the following elements. a. bromine (Br) _______________________________________ _____________________________ b. strontium (Sr) _______________________________________ _____________________________ c. antimony (Sb) _______________________________________ _____________________________ d. rhenium (Re) _______________________________________ _____________________________ e. terbium (Tb) _______________________________________ _____________________________ f. titanium (Ti) _______________________________________ _____________________________ • Noble Gas Notation: Use the nearest noble gas, with added electronic configuration for each element o
Ne: _______________________ o
Mg: ____________________________ or __________________________ Valence Electrons o Valence electrons are defined as the electrons in the outermost orbitals. o They determine the chemical properties, and can be determined using the periodic table. o Kernel: Electrons that occupy the atom’s inner orbitals (All non‐valence electrons) Electron Dot Structures o Valence electrons are involved in chemical bonding o Electron‐dot structure consists of the element’s symbol surrounded by dots representing the atom’s valence electrons. Be N Ne Write the following for each element a. Electron Configuration b. Orbital Pair Diagram c. Lewis Dot Structure N Na Ti P Cl a. b. a. b. a. b. a. b. a. b. c. c. c. c. c.