4 7 Electron Configurations Electron configurations follow the

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4. 7 Electron Configurations Electron configurations follow the order of occupied sublevels on the

4. 7 Electron Configurations Electron configurations follow the order of occupied sublevels on the periodic table. Learning Goal Draw the orbital diagram and write the electron configuration for an element. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Orbital Diagrams Orbital diagrams use boxes to show electrons • are arranged in the

Orbital Diagrams Orbital diagrams use boxes to show electrons • are arranged in the orbitals of an atom. • fill the orbitals and energy levels from lowest to highest energy level. • fill orbitals within the same sublevel one at a time, before pairing the electrons. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Electron Configurations Chemists use a notation called electron configuration to • indicate the placement

Electron Configurations Chemists use a notation called electron configuration to • indicate the placement of electrons in an atom. • show electrons fill energy levels and sublevels in order of increasing energy. • write an abbreviated form using a noble gas to represent all electrons preceding it. Electron Configuration for Carbon Core Chemistry Skill Writing Electron Configurations General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Period 1: Hydrogen and Helium General, Organic, and Biological Chemistry: Structures of Life, 5/e

Period 1: Hydrogen and Helium General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Period 2: Lithium to Neon General, Organic, and Biological Chemistry: Structures of Life, 5/e

Period 2: Lithium to Neon General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Guide to Drawing Orbital Diagrams General, Organic, and Biological Chemistry: Structures of Life, 5/e

Guide to Drawing Orbital Diagrams General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Drawing Orbital Diagrams Nitrogen atoms are found in amino acids, proteins, and nucleic acids.

Drawing Orbital Diagrams Nitrogen atoms are found in amino acids, proteins, and nucleic acids. Draw the orbital diagram for nitrogen. STEP 1 Draw boxes to represent the occupied orbitals. Nitrogen’s atomic number is 7, which means it has seven electrons. For the orbital diagram, we draw boxes to represent the 1 s, 2 s, and 2 p orbitals. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Drawing Orbital Diagrams Nitrogen atoms are found in amino acids, proteins, and nucleic acids.

Drawing Orbital Diagrams Nitrogen atoms are found in amino acids, proteins, and nucleic acids. Draw the orbital diagram for nitrogen. STEP 2 Place a pair of electrons with opposite spins in each filled orbital. First we place a pair of electrons with opposite spins in the 1 s and 2 s orbitals. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Drawing Orbital Diagrams Nitrogen atoms are found in amino acids, proteins, and nucleic acids.

Drawing Orbital Diagrams Nitrogen atoms are found in amino acids, proteins, and nucleic acids. Draw the orbital diagram for nitrogen. STEP 3 Place the remaining electrons in the last occupied sublevel in separate orbitals. Place three remaining electrons in the three separate 2 p orbitals, with arrows drawn in the same direction. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Period 3: Sodium to Argon General, Organic, and Biological Chemistry: Structures of Life, 5/e

Period 3: Sodium to Argon General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Electron Configurations and the Periodic Table The electron configurations of elements are related to

Electron Configurations and the Periodic Table The electron configurations of elements are related to their positions on the periodic table. Different sections or blocks correspond to sublevels s, p, d, and f. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Blocks on the Periodic Table 1. The s block contains elements in Groups 1

Blocks on the Periodic Table 1. The s block contains elements in Groups 1 A (1) and 2 A (2). This means the final one or two electrons are in the s sublevel. 2. The p block consists of elements in Group 3 A (13) to Group 8 A (18). There are six p block elements in each period, because three p orbitals can hold a maximum of six electrons. 3. The d block, which contains transition elements, first appears after calcium (atomic number 20). There are 10 elements in the d block, because five d orbitals can hold a maximum of 10 electrons. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Blocks on the Periodic Table 4. The f block, the inner transition elements, is

Blocks on the Periodic Table 4. The f block, the inner transition elements, is the two rows of elements at the bottom of the periodic table. There are 14 elements in each f block, because seven f orbitals can hold a maximum of 14 electrons. Core Chemistry Skill Using the Periodic Table to Write Electron Configurations General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Guide to Writing Configurations Using Sublevel Blocks Use the sublevel blocks on the periodic

Guide to Writing Configurations Using Sublevel Blocks Use the sublevel blocks on the periodic table to write the electron configuration for chlorine. STEP 1 Locate the element on the periodic table. Chlorine (atomic number 17) is in Group 7 A (17) and Period 3. STEP 2 Write the filled sublevels in order, going across each period. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Guide to Writing Configurations Using Sublevel Blocks Use the sublevel blocks on the periodic

Guide to Writing Configurations Using Sublevel Blocks Use the sublevel blocks on the periodic table to write the electron configuration for chlorine. STEP 3 Complete the configuration by counting the electrons in the last occupied sublevel block. Because chlorine is the fifth element in the 3 p block, there are five electrons in the 3 p sublevel. The electron configuration for chlorine (Cl) is 1 s 22 p 63 s 23 p 5. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Electron Configurations: Period 4 and Above Beginning in Period 4, • the 4 s

Electron Configurations: Period 4 and Above Beginning in Period 4, • the 4 s sublevel fills before the 3 d sublevel, because the 3 d sublevel is slightly lower in energy than the 4 s sublevel. • the 5 s sublevel fills before the 4 d sublevel. • the 6 s sublevel fills before the 5 d sublevel. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Electron Configurations: Period 4 and Above General, Organic, and Biological Chemistry: Structures of Life,

Electron Configurations: Period 4 and Above General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Electron Configurations: Period 4 and Above General, Organic, and Biological Chemistry: Structures of Life,

Electron Configurations: Period 4 and Above General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Study Check Use the sublevel blocks on the periodic table to write the electron

Study Check Use the sublevel blocks on the periodic table to write the electron configuration for selenium. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Solution Use the sublevel blocks on the periodic table to write the electron configuration

Solution Use the sublevel blocks on the periodic table to write the electron configuration for selenium. STEP 1 Locate the element on the periodic table. Selenium is in Period 4, Group 6 A (16). STEP 2 Write the filled sublevels in order, going across each period. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Solution Use the sublevel blocks on the periodic table to write the electron configuration

Solution Use the sublevel blocks on the periodic table to write the electron configuration for selenium. STEP 3 Complete the configuration by counting the electrons in the last occupied sublevel block. Because selenium is the fourth element in the 4 p block, there are four electrons to place in the 4 p sublevel. The electron configuration for selenium (Se) is 1 s 22 p 63 s 23 p 64 s 23 d 104 p 4. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

3 d Sublevel Exceptions • For chromium (Cr), moving one of the 4 s

3 d Sublevel Exceptions • For chromium (Cr), moving one of the 4 s electrons to the 3 d sublevel adds stability with a half-filled d subshell, and the resulting configuration is 4 s 13 d 5. • For copper (Cu), moving one of the 4 s electrons to the 3 d sublevel adds stability with a filled d subshell, and the resulting configuration is 4 s 13 d 10. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Study Check Use the periodic table to give the symbol and name for the

Study Check Use the periodic table to give the symbol and name for the element with the electron configuration of 1 s 22 p 63 s 23 p 64 s 23 d 7. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Solution Use the periodic table to give the symbol and name for the element

Solution Use the periodic table to give the symbol and name for the element with the electron configuration of 1 s 22 p 63 s 23 p 64 s 23 d 7. There are seven electrons in the 3 d sublevel. Thus, the element is cobalt (Co). General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Study Check Write the electron arrangement for the following elements: C Si O General,

Study Check Write the electron arrangement for the following elements: C Si O General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Solution STEP 1 Locate the element on the periodic table. C: atomic number 6,

Solution STEP 1 Locate the element on the periodic table. C: atomic number 6, Period 2, Group 4 A (14) Si: atomic number 14, Period 3, Group 5 A (15) O: atomic number 8, Period 2, Group 6 A (16) General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Solution STEP 2 Write the filled sublevels in order, going across each period. C

Solution STEP 2 Write the filled sublevels in order, going across each period. C 1 s 22 s 2 Si 1 s 22 p 63 s 2 O 1 s 22 s 2 General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.

Solution STEP 3 Complete the configuration by counting the electrons in the last occupied

Solution STEP 3 Complete the configuration by counting the electrons in the last occupied sublevel block. C, the second element in the 2 p block, has two electrons to place in the 2 p sublevel: 1 s 22 p 2. Si, the second element in the 3 p block, has two electrons to place in the 3 p sublevel: 1 s 22 p 63 s 23 p 2. O, the fourth element in the 2 p block, has four electrons to place in the 2 p sublevel: 1 s 22 p 4. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc.