Chapter 5 Electrons In Atoms 5.2 Electron Arrangement in Atoms 5.1 Revising the Atomic Model 5.2 Electron Arrangement in Atoms 5.3 Atomic Emission Spectra and the Quantum Mechanical Model Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

The Quantum Mechanical Model Electron does not have an exact orbit. Atomic Orbital – region of space where there is a high probability of finding an electron. Electron cloud Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Indicates shell occupied by electron n =1,2,3,4,5,6,7 Atomic Orbitals Energy Level (n) Indicates shell occupied by electron n =1,2,3,4,5,6,7 Corresponds to period (row) on periodic table Also called Principal Quantum Number Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Each energy level contains sublevels Atomic Orbitals Sublevels Each energy level contains sublevels Sublevels contain orbitals of different shapes and energies (s,p,d, or f) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

There can be several orbital configurations within a sublevel Atomic Orbitals Sublevels There can be several orbital configurations within a sublevel s – sublevel contains 1 orbital p – sublevel contains 3 orbitals d – sublevel contains 5 orbitals f – sublevel contains 7 orbitals Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Atomic Orbitals Sublevels # of sublevels within an energy level is equal to the principle quantum number For example, n = 1 has 1 sublevel n = 2 has 2 sublevels n = 1, s n = 2, s,p n = 3, s,p,d n = 4, s,p,d,f Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Atomic Orbitals Summary of Principal Energy Levels and Sublevels Number of sublevels Type of sublevel (n2) Maximum number of electrons (2n2) n = 1 1 1s (1 orbital) 2 n = 2 2s (1 orbital), 2p (3 orbitals) 8 n = 3 3 3s (1 orbital), 3p (3 orbitals), 3d (5 orbitals) 18 n = 4 4 4s (1 orbital), 4p (3 orbitals), 4d (5 orbitals), 4f (7 orbitals) 32 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Quantum Numbers The building = atom Apartment Floors = Energy Levels (shells) Specific Apartments = Orbitals (subshells) Residents = Electrons

Electron Configurations Describes location of electrons in an atom Looks like… Titanium: 1s22s22p63s23p64s23d2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Electron Configurations Aufbau Principle Aufbau principle: electrons occupy orbitals of lowest energy first. Each box represents an atomic orbital. Increasing energy 6s 5s 4s 3s 2s 1s 6p 5p 5d 4p 4d 4f 3p 3d 2p Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Electron Configurations Pauli Exclusion Principle Each orbital can only hold 2 electrons. To occupy the same orbital, two electrons must have opposite spins An orbital containing paired electrons is written as . Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Electron Configurations Hund’s rule Orbitals of the same energy(degenerate orbitals) must be occupied by 1 electron before it can be occupied by two electrons. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Electron Configurations Hund’s Rule Three electrons would occupy three orbitals of equal energy as follows. P subshell: Electrons then occupy each orbital so that their spins are paired with the first electron in the orbital. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Electron Configurations Increasing energy 6s 5s 4s 3s 2s 1s 6p 5p 5d 4p 4d 4f 3p 3d 2p Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Electron Configurations in Groups Blocks of Elements Each period on the periodic table corresponds to a principal energy level. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Writing Electron Configurations Sample Problem 5.1 Writing Electron Configurations The atomic number of phosphorus is 15. Write the electron configuration of a phosphorus atom. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Writing Electron Configurations Sample Problem 5.1 Writing Electron Configurations The atomic number of phosphorus is 15. Write the electron configuration of a phosphorus atom. 1s22s22p63s23p3. Note: The superscripts add up to the number of electrons. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

END OF 5.2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.