Atoms and Periodic Properties

Transcription

1 Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten Unit 01 (Chp 6,7): Atoms and Periodic Properties John D. Bookstaver St. Charles Community College St. Peters, MO 2006, Prentice Hall, Inc. Development of the Atomic Model Indivisible empty Identical + stuff space React in electrons nucleus + fixed ratios Development of the Atomic Model Rutherford s atomic model didn t explain properties of matter (color, reactivity, ) Li Na Cu 1

2 white light continuous spectrum prism Atomic Emission Spectra elements discrete lines of E & f helium (He) prism lamp (only specific colors of energy & frequency) Hydrogen Emission Spectrum A mystery for Niels Bohr. (1913 Niels Bohr) Bohr s Shell Model EXCITED state e s absorb (+) energy, move to outer levels (n=2 to n=5) 5 2 E e s emit ( ) energy, move back to inner levels (n=5 to n=2) GROUND state Which transition shows a light wave of the greatest energy? n=5 to n=2 2

3 Photon Energy as Light Waves Distance between same point on adjacent waves is the. wavelength (λ) (m) Number of Waves passing a given point per unit time is the. frequency (ν) (Hz)(s 1 ) λ and ν are inversely proportional All light waves move at the same speed, so which color has more energy? Low Energy R O Y G B I V High Energy Electromagnetic (EM) Spectrum Low Frequency High Frequency (higher E) (higher ν) (shorter λ) All EM waves travel the same speed: the speed of light (c), m/s. c = λν 3

4 Photon (Light) Calculations Given wavelength (λ) of light, one can calculate the energy (E) of 1 photon of that light: m/s J s (constants) c = λν λ, ν (inverse) λ ν (given on Exam) HW p. 253 #14,25ab,26,34 E = hν E, ν (direct) ν E Quantum Mechanical Model (1926 Schrodinger, Plank, de Broglie, etc. ) Heisenberg Uncertainty Principle: The more precisely a particle s motion is known, (wave) (E, λ, ν) the less precisely its position is known. (particle)(probable locations) Schrödinger Wave Equation: s, p, d, f 3-D regions of probability (ORBITALS) in sublevels in each fixed energy level which better explains reactivity. Quantum Mechanical Model Electrons as Waves (instead of particles) electrons occupy only specific levels (shells) of quantized energy (& wavelength & frequency) quantized into specific multiples of wavelengths, nucleus but none in between. 4

5 Development of Atomic Models 1803 Dalton Atomic Theory 1904 Thomson Plum Pudding 1911 Rutherford Nuclear Model 1913 Bohr Shell Model 1926 Quantum Mechanical Model + + Where are the electrons really? 1. (Shell) principle energy level (n) (1,2,3,4 ) 2. (Sub-shell) shape (not rings) s (1) p (3) d (5) f (7) 3. (Orbital) 3-D arranged x y z 4. (Electron) spin up/down HW p. 255 #57ac, 60 Electron Configuration (arrangement) +8 Orbital Notation Oxygen (O) # of e s in each sublevel 1s 2 2s 2 2p 4 energy level (shell, n) sublevel shape (s,p,d,f) 5

6 Electron Configuration (arrangement) +8 Oxygen (O) 1s 2 2s 2 2p 4 6 E-Config? Element? Na 1s 2 2s 2 2p 6 3s 1 How many valence e s? (outer level) Al 1s 2 2s 2 2p 6 3s 2 3p 1 Cl [Ne] 3s 2 3p 5 (noble gas core configuration) d orbital e s are core e s NOT valence e s 1s 2 2s 2 2p 36 3s 2 3p 6 4s 2 3d 10 4p 2 Hund:1 e in equal orbitals before pairing ( ) Pauli Exclusion: no e s same props (opp. spin) ( ) nucleus + (3d fills after 4s) Aufbau: Fill lowest energy orbitals first.? Electron Configuration of Ions Ion (i) F (ii) Ca 2+ (iii) S 2 (iv) Na + (v) Al 3+ E-Con 1s 2 2s 2 2p 6 1s 2 2s 2 2p 6 3s 2 3p 6 1s 2 2s 2 2p 6 3s 2 3p 6 1s 2 2s 2 2p 6 1s 2 2s 2 2p 6 [Ne] [Ar] [Ar] [Ne] [Ne] Which ions are isoelectronic? F, Na +, Al 3+ Ca 2+, S 2 List 3 species isoelectronic with Ca 2+ & S 2. P 3, Cl, Ar, K +, Sc 3+, Ti 4+, V 5+, Cr 6+, Mn 7+ 6

7 Other Aspects of Electron Configs Paramagnetic: species attracted by a magnet (caused by unpaired electrons). Fe: [Ar] 4s 3d Diamagnetic: species repelled by magnets (caused by all paired electrons) Zn: [Ar] 4s 3d ( di- is 2) Other Aspects of Electron Configs d block metals lose their outer s electrons before any core d electrons to form ions. Fe 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 Fe 2+ 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 Fe 3+ 1s 2 2s 2 2p 6 3s 2 3p 6 3d 5 HW p.255 #74 d block (trans. metals) have colored ions b/c light excites e transitions in d orbitals Spectroscopy SPECTROSCOPIC TECHNIQUE EM REGION APPLICATION Microwave Microwave Molecular Structure by molecular Rotation IR Infrared Types of bonds by bond Vibration Vis/UV Atomic Emission Spectra (lines of frequencies/colors) Visible & Ultraviolet Transition of e s between energy levels PES (Photoelectron Spectroscopy) X-ray Ionization of e s shows e configuration WATCH this 6 min Video Explanation of PES at HOME. 7

8 Photoelectron Spectroscopy (PES) Relative # of e s Which peak is H and which is He? higher peak = more e s 1s 2 He 1s 1 H Binding Energy (MJ/mol)...or Ionization Energy (required to remove e s) further left = more energy required (stronger attraction due to more protons) Photoelectron Spectroscopy (PES) Relative # of e s Which peak is H and which is He? higher peak = more e s 2p 6 Ne? 1s 2 1s 2 He 1s 1 Identify the element 2s 2 H & e-config Binding Energy (MJ/mol)...or Ionization Energy (required to remove e s) further left = more energy required (stronger attraction due to more protons) Identify element (A) Ge PES (A) 3d 10 2p 6 3p 6 1s 2 2s 2 3s 2 4s 2 4p 2 n = 1 n = 2 n = 3 n = 4 Identify element (B) K PES (B) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1? 8

9 Write the complete electron configuration of element (X), and identify the element. 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 1 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 1 PES (X) Ga WS 3a 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 1 Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten Unit 1 (Chp 7): Periodic Properties or Periodicity of Trends in Atomic Properties John D. Bookstaver St. Charles Community College St. Peters, MO 2006, Prentice Hall, Inc. Periodic Trends We will explain observed trends in size lose e attract e Atomic (and Ionic) Radius Ionization energy Electronegativity Z eff & shielding (explains ALL periodic trends and properties) 9

10 Z eff & Shielding effective nuclear charge, (Z eff ): Z eff = Z S Z = nuclear charge (+proton s) S = shielding (core e s) attraction shielding, (S): inner core e s shield valence shielding e s from nuclear attraction. Z eff +11 Z = +11 Na atom Z eff = +1 Atomic Radius decreases across a period -due to increasing Z eff (more protons) att. =shield Z eff increases down a group -due to increasing shielding (more energy levels) att. shield =Z eff Ionic Radius e e Na + Cations are smaller than neutral atoms. outermost electron(s) are removed and loses a shell core shell closer to nucleus inner e s shielded ( Z eff ) 10

11 HW p. 292 #13,28 Ionic Radius e e Anions are larger than their parent atoms. electrons are added and repulsions are increased (=Z eff & =shielding) Arrange the following species by increasing size: Ar, K +, Ca 2+, S 2, Cl Ca 2+ < K+ < Ar < Cl < S 2 e Ionization Energy (IE) energy required to remove an electron more energy to remove next electron IE 1 < IE 2 < IE 3, look for a huge jump in IE once all valence e s are removed, the next e is on an inner level with attraction ( shielding & Z eff ). huge jump in IE 4 b/c 4 th e on inner level (must have 3 valence e s) -due to increasing shielding (more energy levels) att. shield =Z eff decreases down a group Trends in First IE increases across a period -due to increasing Z eff (more protons) att. =shield Z eff 11

12 Does this graph support your understanding of IE 1 and the Periodic Table? 5 B & 8O exceptions to trend. Why? Exceptions to 1 st IE Trend 1 st IE tends to increase across period ( Z eff, =shielding) B 2s 2p 1 st IE of B < Be b/c Be 2s The e in 2p orbital of B is higher energy than the e in 2s orbital of Be ; less energy needed to remove 1 st e in B. Exceptions to 1 st IE Trend 1 st IE tends to increase across period ( Z eff, =shielding) O 2s 2p N 2s 2p 1 st IE of O < N b/c The paired e in 2p orbital of O experiences e ---e repulsion requiring less energy to remove 1 st e in O. HW p. 292 #38,46 12

13 Trends in Electronegativity (EN) -ability of an atom to attract electrons when bonded (sharing e s) with another atom. increases across a period -due to increasing Z eff (more protons) decreases down a group att. =shield Z eff -due to increasing shielding att. shield =Z eff Periodic Table Elements arranged by atomic # Periodic Table Metals on the left (80% of all elements) 13

14 Periodic Table Nonmetals on the right (except H) Periodic Table Metalloids border the stair-step (Al is metal) 14

15 ERROR: stackunderflow OFFENDING COMMAND: ~ STACK: