DOCSLIB.ORG

But Not in Text Order

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
But Not in Text Order 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.
Load more

Recommended publications
  • October 16, 2014
    October 16, 2014 Chapter 5: Electrons in Atoms Honors Chemistry Bohr Model Niels Bohr, a young Danish physicist and a student of Rutherford improved Rutherford's model. Bohr proposed that an electron is found only in specific circular paths, or orbits, around the nucleus. Each electron orbit has a fixed energy. Energy levels: the fixed energies of an electron. Quantum: The amount of energy required to move an electron from one energy level to another level. Light Electrons can jump from one energy level to another. The term quantum leap can be used to describe an The modern quantum model grew out of the study of light. 1. Light as a wave abrupt change in energy. 2. Light as a particle -Newton was the first to try to explain the behavior of light by assuming that light consists of particles. October 16, 2014 Light as a Wave 1. Wavelength-shortest distance between equivalent points on a continuous wave. symbol: λ (Greek letter lambda) 2. Frequency- the number of waves that pass a point per second. symbol: ν (Greek letter nu) 3. Amplitude-wave's height from the origin to the crest or trough. 4. Speed-all EM waves travel at the speed of light. symbol: c=3.00 x 108 m/s in a vacuum The speed of light Calculate the following: 8 1. The wavelength of radiation with a frequency of 1.50 x 1013 c=3.00 x 10 m/s Hz. Does this radiation have a longer or shorter wavelength than red light? (2.00 x 10-5 m; longer than red) c=λν 2.
    [Show full text]
  • Lecture #2: August 25, 2020 Goal Is to Define Electrons in Atoms
    Lecture #2: August 25, 2020 Goal is to define electrons in atoms • Bohr Atom and Principal Energy Levels from “orbits”; Balance of electrostatic attraction and centripetal force: classical mechanics • Inability to account for emission lines => particle/wave description of atom and application of wave mechanics • Solutions of Schrodinger’s equation, Hψ = Eψ Required boundaries => quantum numbers (and the Pauli Exclusion Principle) • Electron configurations. C: 1s2 2s2 2p2 or [He]2s2 2p2 Na: 1s2 2s2 2p6 3s1 or [Ne] 3s1 => Na+: [Ne] Cl: 1s2 2s2 2p6 3s23p5 or [Ne]3s23p5 => Cl-: [Ne]3s23p6 or [Ar] What you already know: Quantum Numbers: n, l, ml , ms n is the principal quantum number, indicates the size of the orbital, has all positive integer values of 1 to ∞(infinity) (Bohr’s discrete orbits) l (angular momentum) orbital 0s l is the angular momentum quantum number, 1p represents the shape of the orbital, has integer values of (n – 1) to 0 2d 3f ml is the magnetic quantum number, represents the spatial direction of the orbital, can have integer values of -l to 0 to l Other terms: electron configuration, noble gas configuration, valence shell ms is the spin quantum number, has little physical meaning, can have values of either +1/2 or -1/2 Pauli Exclusion principle: no two electrons can have all four of the same quantum numbers in the same atom (Every electron has a unique set.) Hund’s Rule: when electrons are placed in a set of degenerate orbitals, the ground state has as many electrons as possible in different orbitals, and with parallel spin.
    [Show full text]
  • Principal, Azimuthal and Magnetic Quantum Numbers and the Magnitude of Their Values
    268 A Textbook of Physical Chemistry – Volume I Principal, Azimuthal and Magnetic Quantum Numbers and the Magnitude of Their Values The Schrodinger wave equation for hydrogen and hydrogen-like species in the polar coordinates can be written as: 1 휕 휕휓 1 휕 휕휓 1 휕2휓 8휋2휇 푍푒2 (406) [ (푟2 ) + (푆푖푛휃 ) + ] + (퐸 + ) 휓 = 0 푟2 휕푟 휕푟 푆푖푛휃 휕휃 휕휃 푆푖푛2휃 휕휙2 ℎ2 푟 After separating the variables present in the equation given above, the solution of the differential equation was found to be 휓푛,푙,푚(푟, 휃, 휙) = 푅푛,푙. 훩푙,푚. 훷푚 (407) 2푍푟 푘 (408) 3 푙 푘=푛−푙−1 (−1)푘+1[(푛 + 푙)!]2 ( ) 2푍 (푛 − 푙 − 1)! 푍푟 2푍푟 푛푎 √ 0 = ( ) [ 3] . exp (− ) . ( ) . ∑ 푛푎0 2푛{(푛 + 푙)!} 푛푎0 푛푎0 (푛 − 푙 − 1 − 푘)! (2푙 + 1 + 푘)! 푘! 푘=0 (2푙 + 1)(푙 − 푚)! 1 × √ . 푃푚(퐶표푠 휃) × √ 푒푖푚휙 2(푙 + 푚)! 푙 2휋 It is obvious that the solution of equation (406) contains three discrete (n, l, m) and three continuous (r, θ, ϕ) variables. In order to be a well-behaved function, there are some conditions over the values of discrete variables that must be followed i.e. boundary conditions. Therefore, we can conclude that principal (n), azimuthal (l) and magnetic (m) quantum numbers are obtained as a solution of the Schrodinger wave equation for hydrogen atom; and these quantum numbers are used to define various quantum mechanical states. In this section, we will discuss the properties and significance of all these three quantum numbers one by one. Principal Quantum Number The principal quantum number is denoted by the symbol n; and can have value 1, 2, 3, 4, 5…..∞.
    [Show full text]
  • Vibrational Quantum Number
    Fundamentals in Biophotonics Quantum nature of atoms, molecules – matter Aleksandra Radenovic [email protected] EPFL – Ecole Polytechnique Federale de Lausanne Bioengineering Institute IBI 26. 03. 2018. Quantum numbers •The four quantum numbers-are discrete sets of integers or half- integers. –n: Principal quantum number-The first describes the electron shell, or energy level, of an atom –ℓ : Orbital angular momentum quantum number-as the angular quantum number or orbital quantum number) describes the subshell, and gives the magnitude of the orbital angular momentum through the relation Ll2 ( 1) –mℓ:Magnetic (azimuthal) quantum number (refers, to the direction of the angular momentum vector. The magnetic quantum number m does not affect the electron's energy, but it does affect the probability cloud)- magnetic quantum number determines the energy shift of an atomic orbital due to an external magnetic field-Zeeman effect -s spin- intrinsic angular momentum Spin "up" and "down" allows two electrons for each set of spatial quantum numbers. The restrictions for the quantum numbers: – n = 1, 2, 3, 4, . – ℓ = 0, 1, 2, 3, . , n − 1 – mℓ = − ℓ, − ℓ + 1, . , 0, 1, . , ℓ − 1, ℓ – –Equivalently: n > 0 The energy levels are: ℓ < n |m | ≤ ℓ ℓ E E 0 n n2 Stern-Gerlach experiment If the particles were classical spinning objects, one would expect the distribution of their spin angular momentum vectors to be random and continuous. Each particle would be deflected by a different amount, producing some density distribution on the detector screen. Instead, the particles passing through the Stern–Gerlach apparatus are deflected either up or down by a specific amount.
    [Show full text]
  • Performance of Numerical Approximation on the Calculation of Two-Center Two-Electron Integrals Over Non-Integer Slater-Type Orbitals Using Elliptical Coordinates
    Performance of numerical approximation on the calculation of two-center two-electron integrals over non-integer Slater-type orbitals using elliptical coordinates A. Bağcı* and P. E. Hoggan Institute Pascal, UMR 6602 CNRS, University Blaise Pascal, 24 avenue des Landais BP 80026, 63177 Aubiere Cedex, France [email protected] Abstract The two-center two-electron Coulomb and hybrid integrals arising in relativistic and non- relativistic ab-initio calculations of molecules are evaluated over the non-integer Slater-type orbitals via ellipsoidal coordinates. These integrals are expressed through new molecular auxiliary functions and calculated with numerical Global-adaptive method according to parameters of non-integer Slater- type orbitals. The convergence properties of new molecular auxiliary functions are investigated and the results obtained are compared with results found in the literature. The comparison for two-center two- electron integrals is made with results obtained from one-center expansions by translation of wave- function to same center with integer principal quantum number and results obtained from the Cuba numerical integration algorithm, respectively. The procedures discussed in this work are capable of yielding highly accurate two-center two-electron integrals for all ranges of orbital parameters. Keywords: Non-integer principal quantum numbers; Two-center two-electron integrals; Auxiliary functions; Global-adaptive method *Correspondence should be addressed to A. Bağcı; e-mail: [email protected] 1 1. Introduction The idea of considering the principal quantum numbers over Slater-type orbitals (STOs) in the set of positive real numbers firstly introduced by Parr [1] and performed for the He atom and single- center calculations on the H2 molecule to demonstrate that improved accuracy can be achieved in Hartree-Fock-Roothaan (HFR) calculations.
    [Show full text]
  • The Quantum Mechanical Model of the Atom
    The Quantum Mechanical Model of the Atom Quantum Numbers In order to describe the probable location of electrons, they are assigned four numbers called quantum numbers. The quantum numbers of an electron are kind of like the electron’s “address”. No two electrons can be described by the exact same four quantum numbers. This is called The Pauli Exclusion Principle. • Principle quantum number: The principle quantum number describes which orbit the electron is in and therefore how much energy the electron has. - it is symbolized by the letter n. - positive whole numbers are assigned (not including 0): n=1, n=2, n=3 , etc - the higher the number, the further the orbit from the nucleus - the higher the number, the more energy the electron has (this is sort of like Bohr’s energy levels) - the orbits (energy levels) are also called shells • Angular momentum (azimuthal) quantum number: The azimuthal quantum number describes the sublevels (subshells) that occur in each of the levels (shells) described above. - it is symbolized by the letter l - positive whole number values including 0 are assigned: l = 0, l = 1, l = 2, etc. - each number represents the shape of a subshell: l = 0, represents an s subshell l = 1, represents a p subshell l = 2, represents a d subshell l = 3, represents an f subshell - the higher the number, the more complex the shape of the subshell. The picture below shows the shape of the s and p subshells: (notice the electron clouds) • Magnetic quantum number: All of the subshells described above (except s) have more than one orientation.
    [Show full text]
  • Magnetic Quantum Number: Describes the Orbital of the Subshell  Ms Or S - Spin Quantum Number: Describes the Spin QUANTUM NUMBER VALUES
    ST. LAWRENCE HIGH SCHOOL A JESUIT CHRISTIAN MINORITY INSTITUTION STUDY MATERIAL FOR CHEMISTRY (CLASS-11) TOPIC- STRUCTURE OF ATOM SUBTOPIC- QUANTUM NUMBERS PREPARED BY: MR. ARNAB PAUL CHOWDHURY SET NUMBER-03 DATE: 07.07.2020 ------------------------------------------------------------------------------------------------------------------------------- In chemistry and quantum physics, quantum numbers describe values of conserved quantities in the dynamics of a quantum system. In the case of electrons, the quantum numbers can be defined as "the sets of numerical values which give acceptable solutions to the Schrödinger wave equation for the hydrogen atom". How many quantum numbers exist? A quantum number is a value that is used when describing the energy levels available to atoms and molecules. An electron in an atom or ion has four quantum numbers to describe its state and yield solutions to the Schrödinger wave equation for the hydrogen atom. There are four quantum numbers: n - principal quantum number: describes the energy level ℓ - azimuthal or angular momentum quantum number: describes the subshell mℓ or m - magnetic quantum number: describes the orbital of the subshell ms or s - spin quantum number: describes the spin QUANTUM NUMBER VALUES According to the Pauli Exclusion Principle, no two electrons in an atom can have the same set of quantum numbers. Each quantum number is represented by either a half-integer or integer value. The principal quantum number is an integer that is the number of the electron's shell. The value is 1 or higher (never 0 or negative). The angular momentum quantum number is an integer that is the value of the electron's orbital (for example, s=0, p=1).
    [Show full text]
  • 4 Nuclear Magnetic Resonance
    Chapter 4, page 1 4 Nuclear Magnetic Resonance Pieter Zeeman observed in 1896 the splitting of optical spectral lines in the field of an electromagnet. Since then, the splitting of energy levels proportional to an external magnetic field has been called the "Zeeman effect". The "Zeeman resonance effect" causes magnetic resonances which are classified under radio frequency spectroscopy (rf spectroscopy). In these resonances, the transitions between two branches of a single energy level split in an external magnetic field are measured in the megahertz and gigahertz range. In 1944, Jevgeni Konstantinovitch Savoiski discovered electron paramagnetic resonance. Shortly thereafter in 1945, nuclear magnetic resonance was demonstrated almost simultaneously in Boston by Edward Mills Purcell and in Stanford by Felix Bloch. Nuclear magnetic resonance was sometimes called nuclear induction or paramagnetic nuclear resonance. It is generally abbreviated to NMR. So as not to scare prospective patients in medicine, reference to the "nuclear" character of NMR is dropped and the magnetic resonance based imaging systems (scanner) found in hospitals are simply referred to as "magnetic resonance imaging" (MRI). 4.1 The Nuclear Resonance Effect Many atomic nuclei have spin, characterized by the nuclear spin quantum number I. The absolute value of the spin angular momentum is L =+h II(1). (4.01) The component in the direction of an applied field is Lz = Iz h ≡ m h. (4.02) The external field is usually defined along the z-direction. The magnetic quantum number is symbolized by Iz or m and can have 2I +1 values: Iz ≡ m = −I, −I+1, ..., I−1, I.
    [Show full text]
  • Essential Questions and Objectives
    Essential Questions and Objectives • How does the configuration of electrons affect the atom’s properties? You’ll be able to: – Draw an orbital diagram for an element – Determine the electron configuration for an element – Explain the Pauli exclusion principle, Aufbau principle and Hund’s Rule Warm up Set your goals and curiosities for the unit on your tracker. Have your comparison table out for a stamp Bohr v QMM What are some features of the quantum mechanical model of the atom that are not included in the Bohr model? Quantum Mechanical Model • Electrons do not travel around the nucleus of an atom in orbits • They are found in energy levels at different distances away from the nucleus in orbitals • Orbital – region in space where there is a high probability of finding an electron. Atomic Orbitals Electrons cannot exist between energy levels (just like the rungs of a ladder). Principal quantum number (n) indicates the relative size and energy of atomic orbitals. n specifies the atom’s major energy levels also called the principal energy levels. Energy sublevels are contained within the principal energy levels. Ground-State Electron Configuration The arrangement of electrons in the atom is called the electron configuration. Shows where the electrons are - which principal energy levels, which sublevels - and how many electrons in each available space Orbital Filling • The order that electrons fill up orbitals does not follow the order of all n=1’s, then all n=2’s, then all n=3’s, etc. Electron configuration for... Oxygen How many electrons? There are rules to follow to know where they go ..
    [Show full text]
  • The Principal Quantum Number the Azimuthal Quantum Number The
    To completely describe an electron in an atom, four quantum numbers are needed: energy (n), angular momentum (ℓ), magnetic moment (mℓ), and spin (ms). The Principal Quantum Number This quantum number describes the electron shell or energy level of an atom. The value of n ranges from 1 to the shell containing the outermost electron of that atom. For example, in caesium (Cs), the outermost valence electron is in the shell with energy level 6, so an electron incaesium can have an n value from 1 to 6. For particles in a time-independent potential, as per the Schrödinger equation, it also labels the nth eigen value of Hamiltonian (H). This number has a dependence only on the distance between the electron and the nucleus (i.e. the radial coordinate r). The average distance increases with n, thus quantum states with different principal quantum numbers are said to belong to different shells. The Azimuthal Quantum Number The angular or orbital quantum number, describes the sub-shell and gives the magnitude of the orbital angular momentum through the relation. ℓ = 0 is called an s orbital, ℓ = 1 a p orbital, ℓ = 2 a d orbital, and ℓ = 3 an f orbital. The value of ℓ ranges from 0 to n − 1 because the first p orbital (ℓ = 1) appears in the second electron shell (n = 2), the first d orbital (ℓ = 2) appears in the third shell (n = 3), and so on. This quantum number specifies the shape of an atomic orbital and strongly influences chemical bonds and bond angles.
    [Show full text]
  • Unit 3 Electrons and the Periodic Table
    UNIT 3 ELECTRONS AND THE PERIODIC TABLE Chapter 5 & 6 CHAPTER 5: ELECTRONS IN ATOMS WHAT ARE THE CHEMICAL PROPERTIES OF ATOMS AND MOLECULES RELATED TO? • ELECTRONS! • Number of valence electrons • How much an atom wants to “gain” or “lose” electrons • How many electrons “gained” or “lost” ELECTRON HISTORY • Dalton’s Model • Didn’t even know of electrons or charge – just ratios of atoms. • Thomson’s Model • ELECTRONS EXIST!!!! • Where are they? No clue. • Plum Pudding? • Rutherford’s Model • Gold Foil Experiment • Electrons are found outside the nucleus. • Now knows where they are, but still doesn’t know how they are organized. Rutherford’s model BOHR’S MODEL • Electron’s are found in energy levels. Quantum: Specific energy values that have exact values in between them. • Pictured the atom like a solar system with electrons “orbiting” around the nucleus. • Each orbit path associated with a particular energy. • Now a better understanding of how electrons are organized, but it still isn’t quite correct. QUANTUM MECHANICAL MODEL ERWIN SCHRODINER (1926) • Electrons are found in regions of empty space around the nucleus. “electron clouds”. • Shape of the region corresponds to different energy levels. • Shape of the region represents the probability of the electron’s location 90% of the time. • PROBLEM? These are still called “atomic orbitals”. SCHRODINGER’S MODEL • Electrons are “wave functions”. • We can’t actually know exactly where an electron is at any moment. • We can know a probability of an electrons location based on its energy. • Ex: a windmill blade ATOMIC ORBITALS • Shape describing the probability of finding an electron at various locations around the nucleus.
    [Show full text]
  • CHM 110 - Electron Configuration (R14)- ©2014 Charles Taylor 1/5
    CHM 110 - Electron Configuration (r14)- ©2014 Charles Taylor 1/5 Introduction We previously discussed quantum theory along with atomic orbitals and their shapes. We're still missing some pieces of the puzzle, though. How do electrons in an atom actually occupy the atomic orbitals. How does this arrangement affect the properties of an atom and the ways atoms bond with each other? We will now discuss how an atom's electrons are arranged in atomic orbitals. Knowing a bit about this will help us figure out how atoms bond. The Pauli Exclusion Principle We have described (and drawn) atomic orbitals. But how many electrons can an atomic orbital hold? The answer lies in the quantum numbers, specifically the fourth quantum number. The first three quantum numbers (the principal quantum number, the angular momentum quantum number, and the magnetic quantum number) select the atomic orbital. For example, let's look at a set of quantum numbers of an electron: n = 2 ; l = 1 ; ml = 0 What do these three quantum numbers tell us about this electron? We're told that the electron is in the second energy level (n = 2), that the electron is in one of the "p" orbitals (l = 1), and we're told the orientation of the "p" orbital the electron is in. But to specify the exact electron, we need the fourth quantum number- the spin quantum number. Recall that this quantum number can have only two values (+½ and -½) and that no two electrons in the same atom can have the same set of four quantum numbers.
    [Show full text]