Subshells and Orbitals

Subshells and Orbitals Timberlake LecturePLUS 2000 Quantum Mechanics Describes the arrangement of electrons in atoms in terms of: Main or principal energy levels (n) Energy subshells Orbitals (space occupied within the atom) Timberlake LecturePLUS 2000 Principal Energy Levels (n) Contain electrons that are  Close in energy  Similar distance from nucleus  Have values of n = 1, 2, 3, 4, 5, 6…..  Maximum number of electrons = 2n2 n =1 n =2 n=3 2(1)2 = 2 2(2)2 =8 Timberlake LecturePLUS 2000 Energy Levels (Shells) • A group of electrons in an atom all having the same principal quantum number (n) n = 1, 2, 3, … • The first shell (n = 1) is lowest in energy, 2nd level next and so on 1<2<3<4 • The number of electron in each shell is limited to 2n2 n=1 n=2 2n2 = 2 Timberlake LecturePLUS____ 2n2 = 2000 Energy Levels for Electrons Some possible electron transitions for the first three energy levels are shown below. The negative value means that the electron in the atom has a lower energy than a free electron Energy Level Energy, E n=3 ___________________ (-) 2.420 x 1019 J n=2 __________________ (-) 5.445 x 1019 J n=1 __________________ 2000 2.178 x 1018 J (-) Timberlake LecturePLUS Learning Check S1 A. What energy change (J) takes place when an electron in a hydrogen atom moves from the first (n=1) to the second shell (n=2)? B. What energy change (J) takes place when the electron moves from the third shell to the second shell? Timberlake LecturePLUS 2000 Solution S1 A. What energy change takes place when an electron in a hydrogen atom moves from the first (n=1) to the second shell (n=2)? 1.634 x 10-18 J of energy must be absorbed. B. What energy change takes place when the electron moves from the third shell to the second shell? (-5.445 x 10-19J ) - (2.2420 x 10-19 J) = -3.025 x 1019J will be emitted as electron falls from a higher to a lower energy state Timberlake LecturePLUS 2000 Subshells  Energy sublevels within energy level  All electrons in a subshell have the same energy  Designated s, p, d, f ..  Sublevel energy: s