Electronic Structure of the Atom

Recall: Electrons are organized in shells Electrons are organized in shells 1 st shell 1 st shell 2 nd shell 2 nd shell 3 rd shell 3 rd shell 4 th shell 4 th shell 2 e - 8 e - 18 e - 32 e - Electrons in an atom can possess only specific amounts of energy called ENERGY LEVELS Electrons in an atom can possess only specific amounts of energy called ENERGY LEVELS

Orbitals are the actual region of space occupied by an electron in a particular energy level. Energy Level Diagram for Hydrogen Energy n = 4 n = 3 n = 2 n = 1 1s 2s 3s 4s4p 3p 2p 3d 4d4f Shell is the set of all orbitals having the same n-value. Subshell is the set of orbitals of the same type. (same n-value and orbital type) 1 st shell 2 nd shell 3 rd shell 4 th shell 2p subshell 3d subshell 4p subshell 4f subshell

Energy Level Diagram for Polyelectronic atoms Energy n = 4 n = 3 n = 2 n = 1 1s 2s 3s 4s 4p 3p 2p 3d 4dRules: n = 5 5s 5p 5d n = 6 6s 6p 4f 1.For a given n-value, there are ‘n’ different types of orbitals. 2.An ‘s’ subshell has 1 orbital A ‘p’ subshell has 3 orbitals A ‘d’ subshell has 5 orbitals An ‘f’ subshell has 7 orbitals

Energy Level Diagram for Polyelectronic atoms Energy n = 4 n = 3 n = 2 n = 1 1s 2s 3s 4s 4p 3p 2p 3d 4d Rules Continued: n = 5 5s 5p 5d n = 6 6s 6p 4f 3.Electrons are added to the lowest energy level first. (note: 4s has lower energy than 3d, 5s lower than 4d, etc) 4.A maximum of 2 electrons can be placed in each orbital. Eg: 1s = 2e - 2s = 2e - 2p = 6e - 3d = 10e - 1s 2p 2s 3d

Mr. Annandale, how do you expect us to remember the order of the all the different subshells and their energy levels? 1.Draw a simple chart of the different subshells. 2.Draw diagonal arrows upwards from right to left. 7s 2s 3s 4s 5s 6s 1s 7p 2p 3p 4p 5p 6p 7d 3d 4d 5d 6d 4f 5f 6f

Writing Electron Configurations of Atoms and Ions: Example: H 1 e - H (1s 1 ) He 2 e - He (1s 2 ) Li 3 e - Li (1s 2 2s 1 ) N 7 e - Na 11 e - Na (1s 2 2s 2 2p 6 3s 1 ) N (1s 2 2s 2 2p 3 ) P 15 e - P (1s 2 2s 2 2p 6 3s 2 3p 3 )