Topics covered in Chap 6 BUT NOT IN TEXT ORDER 6.1 The wave nature of Light 6.5 Quantum Mechanics & Atomic Orbitals 6.6 Representation of Orbitals 6.7 Many-Electron Atoms 6.8 Electron Configurations 6.9 Electron Configurations and the Periodic Table ATOMIC PARTICLES Name Charge Proton +1 Neutron 0 Electron -1 WHY ? How electrons are distributed outside the nucleus is important because they determine chemical behavior Electrons Act Like Magnetics Atomic Structure 1. CENTER CORE ……….NUCLEUS Contains NUCLEONS (PROTONS / NEUTRONS) 2. OUTERCORE …………ELECTRONS ATOMIC SYSTEM Simular To SOLAR SYSTEM PLANETS REVOLVE AROUND THE SUN IN ORBITS Solar System Electronic Structure of Atoms ATOMIC SYSTEM SIMULAR TO SOLAR SYSTEM ELECTRONS REVOLVE AROUND THE NUCLEUS IN ORBITS Atomic System Model Effective Nuclear Charge Electrons are attracted to the nucleus The attraction depends on three things 1. Magnitude of the nuclear charge 2. Distance to nucleus 3. Repulsions due to other electrons (shielding or screening effect ORBITALS & SUBORBITALS There are 7 (SEVEN) Major ORBITALS Check out the Periodic Table How Many Periods in the Periodic Table ? The 7 (SEVEN) Major Levels ARE SUBDIVIDED The SUBLEVELS Are Called S, P, D, F, G … Order of Filling The S, P, D, F, G … SUBLEVELS Are further subdivided as follows: S Only one - 1 P Three of them - 3 D Five of them - 5 F Seven of them - 7 etc What is the next number ? SHAPE of ORBITALS • What is an Orbital ? • What do the Orbitals look like ? Coordinate System S Orbital in 3 dimension S Orbitals . The P orbitals are aligned along the three Cartesian coordinates ( x, y, z ) NUMBER OF ELECTRONS ACCOMMODATED IN ELECTRON SHELLS AND SUBSHELLS ELECTRON SUBSHELLS ORBITALS NUMBER SHELL AVAILABLE AVAILABLE ELECTRONS 1 S 1 2 2 S 1 2 P 3 6 S 1 2 3 P 3 6 D 5 10 1st How MANY ELECTRONS ? • For a NEUTRAL Atom, the Number of ELECTRONS is equal to the Atomic Number (which is the number of PROTONS) • For an ION, the Number of ELECTRONS is INCREASED for Anions & Decreased for Cations by Charge on ION How MANY ELECTRONS ? H ____ H+ ____ H- ____ O ____ O- ____ O-2 ____ Fe ____ 2nd , What is the ELECTRON CONFIGURATION • The AUFBAU PRINCIPLE guides the filling order of orbitals • Electrons fill orbitals Closest to nucleus First Aufbau Principle: Lower energy orbitals fill first. Increasing Energy Increasing Core Orbitals only 1s hold two [He] 2s 2p electrons, [Ne] 3s 3p 3d [Ar] and each 4s 4p 4d 4f [Kr] should 5s 5p 5d 5f [Xe] have 6s 6p 6d [Rn] different 7s 7p spin. GROUND H (1 e ) 1S 1 STATE He (2 e ) 2 1S ELECTRON 2 1 Li (3 e ) 1S 2S CONFIGURATION Be (4 e ) 1S 2 2S 2 B (5 e) 1S 2 2S 2 2P 1 C (6 e) 1S 2 2S 2 2P 2 N (7 e) 1S 2 2S 2 2P 3 O (8 e) 1S 2 2S 2 2P 4 F (9 e) 1S 2 2S 2 2P 5 Ne (10e) 1S 2 2S 2 2P 6 Condensed Electron Configuratio Li [He] 2 s 1 Na [Ne] 3s 1 K [Ar] 4 s 1 Rb ????????? What is the last electron in Cs ? Some Anomalies Anomalies occur because the 4 s and 3 d orbitals are very close in energy Anomalous Electron Configurations These result from the unusual stability of half–filled and fully filled subshells. Chromium should be [Ar] 4 s 2 3 d 4 but is [Ar] 4 s 13 d 5 Copper should be [Ar] 4 s 2 3 d 9, but is [Ar] 4 s 13 d 10 Electrons in the Periodic Chart ISOElectronic Atoms or ions that have the same number of electrons and therefore the same ground state electron configuration. Which of the following are isoelectronic? C ? Cl – Mn 2+ B – Ar Zn Fe 3+ Ge 2+ SAMPLE EXERCISE 6.8 • Electron Configurations for a Group • What is the characteristic valence electron configuration of a group of elements ? • What are valence electrons ? What is the characteristic valence electron configuration of the group 7A elements, the halogens? The 1 st member of the halogen group is fluorine F(9 e) 1S 2 2S 2 2P 5 The condensed electron configuration is F [He] 2S 2 2P 5 For chlorine, the 2 nd halogen, Cl (17 e) 1S 2 2S 2 2P 6 3S 2 3P 5 Condensed is Cl [Ne] 3s 2 3P 5 The characteristic valence electron configuration of a halogen is ns 2np 5 where n ranges from 2 in the case of fluorine to 6 in the case of astatine. PRACTICE EXERCISE Which family of elements is characterized by an ns 2np 2 electron configuration in the outermost occupied shell? Answer: ? Break for Exam 2 DISCRIPTION OF ELECTRONS 1. HOW MANY ARE THERE ? 2. ELECTRON CONFIGURATION Follows AUFBAU PRINCIPLE 3. ORBITAL DIAGRAM Follows HUND ’S RULE HUND ’S RULE Electrons Remain UNPAIRED As Long As Possible Electrons Act Like Magnetics Therefore have direction UNPAIRED Electrons The Most Stable Arrangement of Electrons is that with the Maximum Number of UNPAIRED Electrons, all with the SAME Spin Direction ORBITAL DIAGRAMS 1S 2S 2P 3S H ( ↑ ) ( ) ( ) ( ) ( ) ( ) He ( ↑↓ ) ( ) ( ) ( ) ( ) ( ) Li ( ↑↓ ) (↑ ) ( ) ( ) ( ) ( ) Be ( ↑↓ ) ( ↑↓ ) ( ) ( ) ( ) ( ) B ( ↑↓ ) ( ↑↓ ) (↑ )( ) ( ) ( ) C ( ↑↓ ) ( ↑↓ ) (↑ )( ↑ )( ) NOTE! N ( ↑↓ ) ( ↑↓ ) (↑ )( ↑ )(↑) NOTE! Hund’s Rule How many unpaired electrons for atomic (a) Nitrogen (b) Phosphorus (c) Bismuth N(7e) 1s2 2s22p3 P (15e) 1s22s22p6 3s23p3 Bi (83e) 1s22s22p63s23p64s23d10 4p65s24d10 5p6 6s2 4ƒ 14 5d10 6p3 DISCRIPTION OF ELECTRONS 1. HOW MANY Electrons ? 2. ELECTRON Configuration Follows AUFBAU Principle 3. ORBITAL Diagram Follows HUND’s Rule 4. QUANTUM NUMBERS (FOUR) Follows PAULI Principle Symbols & Meanings Mass number (number of protons + neutrons) 12 C Symbol of element 6 Atomic number (number of protons) ELECTRON Configuration Number of electrons Electron Configuration H 1 1S 1 QUANTUM NUMBERS (FOUR) AN ORBITAL IS DESCRIBED BY A SET OF FOUR QUANTUM NUMBERS n l m s denotes the number Denotes the of electrons Principle 1 S 2 Quantum Number denotes the Angular Momentum Quantum Number QUANTUM NUMBERS (Four) n l m s n = 1, 2, 3, 4, 5, 6, or 7 l = n – 1, n – 2, …. m = - l to + l S = + ½ or – ½ N The principal quantum number, n, describes the energy level of the orbital. The values of n are integers n = 1, 2, 3, 4, 5, 6, or 7 NUMBER l l = n – 1, n – 2, …. If lll = 0 1 2 3 4 5 Orbital is s p d f g h l 000 S Only one - 1 111 P Three of them - 3 222 D Five of them - 5 333 F Seven of them - 7 Azimuthal Quantum Number , l The second quantum number defines the shape { s, p, d, f ) of the orbital. Values of l are integers ranging from 0 to n − 1. Value of l 0 1 2 3 Type of orbital s p d f Angular Momentum Quantum Number If lll is Orbital is 0 s 1 p 2 d 3 f 4 g , ml The third quantum number describes the different orbital types within a shell called subshells ml are integers ranging from -l to + l l l. − ≤ ml ≤ l m S 000 0 P 111 -1 0 1 D 222 -2 -1 0 1 2 F 333 -3 -2 -1 0 1 2 3 Magnetic Quantum Number {m =- l to + l If l = 0 m = 0 If l = 1 m = - 1 0 + 1 If l = 2 m = -2 - 1 0 + 1 +2 Spin Quantum Number, ms The fourth quantum number. The spin quantum number has only two values +1/2 and −1/2. Quantum Numbers H(1 e) 1s 1 (↑ ) n = 1 l = 0 m = 0 s = ½ Notation: 1 0 0 ½ Pauli Exclusion Principle No two electrons in the same atom can have identical sets of quantum numbers. Quantum Numbers He (2) 1s 2 (↑ ↓ ) n = 1 1 l = 0 0 m = 0 0 s = ½ - ½ Quantum Numbers Li (3) 1s 2 2s 1 (↑↓ ) ( ↓) n = 1 1 2 l = 0 0 0 m = 0 0 0 s = ½ -½ -½ Quantum Numbers C (6) 1s 2 2s 2 2p 2 (↑↓ ) ( ↑↓ ) ( ↑) (↑ ) ( ) n = 1 1 2 2 2 2 l = 0 0 0 0 1 1 m = 0 0 0 0 -1 0 s = ½-½ ½-½ ½ ½ Quantum Numbers N (7) 1s 2 2s 2 2p 3 (↑↓ ) ( ↑↓ ) ( ↑) (↑ ) ( ↑ ) n = 1 1 2 2 2 2 2 l = 0 0 0 0 1 1 1 m = 0 0 0 0 -1 0 +1 s = ½-½ ½-½ ½ ½ ½ Quantum Numbers Ne (10) 1s 2 2s 2 2p 6 (↑ ↓ ) ( ↑ ↓) (↓↑ ) (↓ ↑ ) ( ↓ ↑) n 1 1 2 2 2 2 2 2 2 2 l 0 0 0 0 1 1 1 1 1 1 m 0 0 0 0 -1 -1 0 0 +1 +1 s ½-½ ½-½ ½-½ ½-½ ½-½ Energy Promotes Electron(s) to Higher Energy Level Light and Electromagnetic Radiation Where Does Energy Come From ? Light is a form of energy Light exhibits properties that have characteristics of discrete particles and characteristics of waves. Electromagnetic Radiation Wavelength (λ) given in distance (meters) Frequency (ν) given in reciprocal time (s –1) speed of light C = speed of light ( a constant) C= 3.00 x 10 8 meters / second λ = wavelength (distance. e.g., meters ) ν = frequency (measured in reciprocal time) Electromagnetic Radiation Wavelength x Frequency = Speed of light λ (m) x ν (s –1) = c (m s –1) RELATIONSHIP BETWEEN C λλλ and ννν C = λλλ x ννν UNITS Solve Problems !! meters 1 = meters × sec sec Which wave has the higher frequency? The lower wave has a longer wavelength (greater distance between peaks). The lower wave has the lower frequency, and the upper one has the higher frequency RELATIONSHIP BETWEEN C λ and ν If λ = 1000 meters (AM Radio) what is the frequency ( ννν ) of radiation ? C = λλλ x ννν meters 1 00.3 x10 8 = 1000 meters × ? sec sec C 3.00x10 8 m / s ν = = = 3.00 x 10 5 sec 1- λ 1000 m A laser used in eye surgery to fuse detached retinas produces radiation with a wavelength of 640.0 nm.