Electronic Configurations of Atoms Valence electrons are electrons on the outermost shell of the atom. ecronc Configurations of the Elements of the First and Second Rows Element Configuration Valence Electrons H He 2 2 山 122 Be 1222 B 12222p 3 1s22s22p2p N 12222p2p2n 0 122222 F 12222p2p2p月 Ne 12222p2 2013 Pearson Education,Inc. Chapter 1 6
© 2013 Pearson Education, Inc. Electronic Configurations of Atoms • Valence electrons are electrons on the outermost shell of the atom. Chapter 1 6
Electronic Configurations 。The aufbau principle Relative orbital energies states to fill the lowest 一2p,-2p一2p energy orbitals first -25 Hund's rule states that energy when there are two or more orbitals of the same energy (degenerate),electrons will -1s go into different orbitals rather than pairing up in the same orbital. 2013 Pearson Education,Inc. Chapter 1 7
© 2013 Pearson Education, Inc. Electronic Configurations • The aufbau principle states to fill the lowest energy orbitals first. • Hund’s rule states that when there are two or more orbitals of the same energy (degenerate), electrons will go into different orbitals rather than pairing up in the same orbital. Chapter 1 7
lonic Bonding To obtain a noble gas configuration (a full valence shell),atoms may transfer electrons from one atom to another. The atoms,now bearing opposite charges, attract each other,forming an ionic bond. Li一f: Li+ 浴、 Li+:F: electron transfer He configuration Ne configuration ionic bond 2013 Pearson Education.Ine 2013 Pearson Education,Inc. Chapter 1 8
© 2013 Pearson Education, Inc. Ionic Bonding • To obtain a noble gas configuration (a full valence shell), atoms may transfer electrons from one atom to another. • The atoms, now bearing opposite charges, attract each other, forming an ionic bond. Chapter 1 8
Covalent Bonding Electrons are shared between the atoms to complete the octet. When the electrons are shared evenly,the bond is said to be nonpolar covalent,or pure covalent. When electrons are not shared evenly between the atoms,the resulting bond will be polar covalent. H(:○H nonpolar polar covalent bond covalent bond D2013 Pearson Education.Ing 2013 Pearson Education,Inc. Chapter 1 9
© 2013 Pearson Education, Inc. Covalent Bonding • Electrons are shared between the atoms to complete the octet. • When the electrons are shared evenly, the bond is said to be nonpolar covalent, or pure covalent. • When electrons are not shared evenly between the atoms, the resulting bond will be polar covalent. Chapter 1 9
Lewis Structures CHa NH3 H Nitrogen:5 e Carbon:4 e 3 H@1 e ea:3e …H 4 H@1 e ea:4e H H 8e 8e H H20 Cl2 Oxygen:6 e 2 H@1 e ea:2e …0…H 2 Cl @7 e ea:14 e 8e :C1C 2013 Pearson Education,Inc. Chapter 1 10
© 2013 Pearson Education, Inc. CH4 NH3 H2O Cl2 Lewis Structures C H H H H N H H H H O H Cl Cl Carbon: 4 e 4 H@1 e ea: 4 e 8 e Nitrogen: 5 e 3 H@1 e ea: 3 e 8 e Oxygen: 6 e 2 H@1 e ea: 2 e 8 e 2 Cl @7 e ea: 14 e Chapter 1 10