unit 3: atomic structure chemistry basics of the atom subatomic particle charge location in the atom...

Unit 3: Atomic Structure Chemistry

Basics of the Atom Subatomic Particle Charge Location in the Atom Mass a.m.u.: unit used to measure mass of atoms atomic mass unit proton neutron electron 1+ 0 1 in nucleus around nucleus ~ 1 a.m.u. ~ 0 a.m.u.

atomic number: -- To find net charge on an atom, consider ____ and ____. mass number: # of p + the whole number on Periodic Table determines identity of the atom (# of p + ) + (# of n 0 ) 10 Ne 20.1797 p+p+ ee (It is NOT on the Table.)

When I see a cation, I see a positive ion; ion: anion: a () ion cation: a (+) ion -- a charged atom more e than p + formed when atoms gain e -- more p + than e formed when atoms lose e a n ions negativeions. are I think that that is, I C ion. A +

Other Mnemonic Devices Metals form positive ions Cations are pawsitive

19 Description Net Charge Atomic Number Mass Number Ion Symbol 15 p + 16 n 0 18 e 38 p + 50 n 0 36 e 18 e 1+ 39 Te 2 128 K+K+ Sr 2+ P 3 88 31 15 3 38 52 2 2+ 76 n 0 52 p + 54 e 20 n 0 19 p +

protium Isotopes: different varieties of an elements atoms -- have diff. #s of n 0 ; thus, diff. mass #s some are radioactive; others arent Isotope H1 Mass p+p+ n0n0 Common Name H2 H3 tritium deuterium 1 2 3 10 11 12 C12 atomsC14 atoms All atoms of an element react the same chemically. 6 p + 6 n 0 stable 6 p + 8 n 0 radioactive

Complete Atomic Designation I 53 125 gives very precise info about an atomic particle mass # atomic # charge (if any) element symbol Goiter due to lack of iodine iodine is now added to salt

Protons Complete Atomic Designation 92 NeutronsElectrons 34 11 146 45 12 92 36 10 59 27 3+ Co 37 17 Cl 557+ Mn 25 238 92 U 23 11 + Na 79 34 2 Se 201817 301825 322427

- or -particles, rays Radioactive Isotopes: Nucleus attempts to attain a lower energy state by releasing extra energy as __________. e.g., half-life: the time needed for of a radioactive sample to decay into stable matter have too many or too few n 0 radiation e.g., C14: half-life is 5,730 years decays into stable N14

Years from now 0 g of N14 present 5,730 11,460 120 60 30 15 7.5 0 Say that a 120 g sample of C-14 is found today g of C14 present 17,190 22,920 60 90 105 112.5 = C14 = N14

Half Life Graph (Sr-90 Activity)

Average Atomic Mass (AAM) This is the weighted average mass of all atoms of an element, measured in a.m.u. For an element with isotopes A, B, etc.: AAM = Mass A (% A) + Mass B (% B) + (use the decimal form of the % e.g., use 0.253 for 25.3%) % abundance Ti has five naturally- occurring isotopes

Lithium has two isotopes. Li-6 atoms have mass 6.015 amu; Li-7 atoms have mass 7.016 amu. Li-6 makes up 7.5% of all Li atoms. Find AAM of Li. AAM = Mass A (% A) + Mass B (% B) AAM = 6.015 amu (0.075) + 7.016 amu AAM = 6.94 amu (0.925) AAM = 0.451 amu + 6.490 amu Li batteries ** Decimal number on Table refers to molar mass (in g) OR AAM (in amu). 6.02 x 10 23 atoms 1 average atom

Isotope Si-28 % abundance 27.98 amu92.23% Mass Si-29 Si-30 28.98 amu4.67% AAM = M A (% A) + M B (% B) + M C (% C) 3.10% ? = 27.98 (0.9223) + 28.98 (0.0467) + X (0.031)28.086 28.086 = 25.806 + 1.353 + 0.031X 28.086 = 27.159 + 0.031X 0.927 = 0.031X 0.031 X = M Si-30 = 29.90 amu

Historical Development of the Atomic Model Greek model of atom Greeks (~400 B.C.E.) Matter is discontinuous (i.e., grainy). Democritus & Leucippus atomos = uncuttable or indivisible Solid and INDESTRUCTABLE

Hints at the Scientific Atom ** Antoine Lavoisier: law of conservation of mass ** Joseph Proust (1799): law of definite proportions: every compound has a fixed proportion e.g.,water.. chromium (II) oxide. 8 g O : 1 g H 13 g Cr : 4 g O mass R = mass P

Hints at the Scientific Atom (cont.) ** John Dalton (1803): 8 g Oe.g., water.. chromium (II) oxide. hydrogen peroxide... chromium (VI) oxide 1 g H: 16 g O1 g H: 13 g Cr4 g O: 13 g Cr12 g O: 2 3 law of multiple proportions: When two different compounds have same two elements, equal mass of one element results in integer multiple of mass of other

1. Elements are made of indivisible particles called atoms. 2. Atoms of the same element are exactly alike; in particular, they have the same mass. Isotopes! John Daltons Atomic Theory (1808) 3. Compounds are formed by the joining of atoms of two or more elements in fixed, whole number ratios. e.g.,1:1, 2:1, 1:3, 2:3, 1:2:1 Daltons model of atom Atoms are divisible NaCl, H 2 O, NH 3, Fe 2 O 3, C 6 H 12 O 6

** William Crookes (1870s): Rays causing shadow were emitted from cathode. Maltese cross CRT radar screen television computer monitor

J.J Thomson (~1900) J.J. Thomson discovered that cathode rays are deflected by electric and magnetic fields J.J. Thomson () particles electrons + + + + + + electric field lines cathode rays phosphorescent screen Crookes tube

William Thomson (a.k.a., Lord Kelvin): Since atom was known to be electrically neutral, he proposed the plum pudding model. Lord Kelvin Thomsons plum pudding model -- Equal quantities of (+) and () charge distributed uniformly in atom. -- (+) is ~2000X more massive than () plum pudding + + + + + + + + + + +

Ernest Rutherford (1909) Gold Leaf Experiment Beam of -particles (+) directed at gold leaf surrounded by phosphorescent (ZnS) screen. -source lead block ZnS screen gold leaf particle beam

Most -particles passed through, some angled slightly, and a tiny fraction bounced back. Conclusions: 1. Atoms are mostly empty space (+) particles are concentrated at center nucleus = little nut () particles orbit nucleus 2. 3.

N Rutherfords Model Thomsons Plum Pudding Model Daltons (also the Greek) Model + + + + + + + + + + +

Thomsons Plum Pudding Model + + + + + + + + + + +

N Rutherfords Model

And now we know of many other subatomic particles: Chadwick ** James Chadwick discovered neutrons in 1932 n 0 have no charge and are hard to detect purpose of n 0 = stability of nucleus quarks, muons, positrons, neutrinos, pions, etc. photo from liquid H 2 bubble chamber

Discovery of the Neutron James Chadwick bombarded beryllium-9 with alpha particles, carbon-12 atoms were formed, and neutrons were emitted. + + Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 764 *Walter Boethe

Recent Atomic Models Max Planck (1900): Proposed that amounts of energy are quantizedquantized only certain values are allowed Niels Bohr (1913): e can possess only certain amounts of energy, and can therefore be only certain distances from nucleus. e found here e never found here planetary (Bohr) model N

Bohr Atom The Planetary Model of the Atom

Bohrs Model Nucleus Electron Orbit Energy Levels

quantum mechanical model electron cloud model charge cloud model Schroedinger, Pauli, Heisenberg, Dirac (up to 1940): According to the QMM, we never know for certain where the e are in an atom, but the equations of the QMM tell us the probability that we will find an electron within a certain distance from the nucleus.

Electron Cloud Model Orbital (electron cloud) instead of orbits Region in space where there is 90% probability of finding an electron Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Electron Probability vs. Distance Electron Probability (%) Distance from the Nucleus (pm) 100150200250500 0 10 20 30 40 Orbital 90% probability of finding the electron

Models of the Atom Review Daltons model (1803) Thomsons plum-pudding model (1897) Rutherfords model (1909) Bohrs model (1913) Charge-cloud model (present) Dorin, Demmin, Gabel, Chemistry The Study of Matter, 3 rd Edition, 1990, page 125 Greek model (400 B.C.) + - - - - - e e e + + + + + + + + e ee e e e e "In science, a wrong theory can be valuable and better than no theory at all." - Sir William L. Bragg

Models of the Atom Timeline Daltons model (1803) Thomsons plum-pudding model (1897) Rutherfords model (1909) Bohrs model (1913) Charge-cloud model (present) Dorin, Demmin, Gabel, Chemistry The Study of Matter, 3 rd Edition, 1990, page 125 Greek model (400 B.C.) 1800 1805..................... 1895 1900 1905 1910 1915 1920 1925 1930 1935 1940 1945 1803 John Dalton pictures atoms as tiny, indestructible particles, with no internal structure. 1897 J.J. Thomson, a British scientist, discovers the electron, leading to his "plum-pudding" model. He pictures electrons embedded in a sphere of positive electric charge. 1904 Hantaro Nagaoka, a Japanese physicist, suggests that an atom has a central nucleus. Electrons move in orbits like the rings around Saturn. 1911 New Zealander Ernest Rutherford states that an atom has a dense, positively charged nucleus. Electrons move randomly in the space around the nucleus. 1913 In Niels Bohr's model, the electrons move in spherical orbits at fixed distances from the nucleus. 1924 Frenchman Louis de Broglie proposes that moving particles like electrons have some properties of waves. Within a few years evidence is collected to support his idea. 1926 Erwin Schrdinger develops mathematical equations to describe the motion of electrons in atoms. His work leads to the electron cloud model. 1932 James Chadwick, a British physicist, confirms the existence of neutrons, which have no charge. Atomic nuclei contain neutrons and positively charged protons. + - - - - - e e e + + + + + + + + e ee e e e e

ENERGY (HEAT, LIGHT, ELEC., ETC.) Light When all e are in lowest possible energy state, an atom is in the ____________. ground state e.g., He: 2 e -, both in 1 st energy level If right amount of energy is absorbed by an e , it can jump to a higher energy level. This is an unstable, momentary condition called the ____________. excited state e.g.,He: 1 e - in 1 st E level, 1 e - in 2 nd E level

When e falls back to a lower-energy, more stable orbital (it might be the orbital it started out in, but it might not), atom releases the right amount of energy as light. EMITTED LIGHT Any-old-value of energy to be absorbed or released is NOT OK. This explains the lines of color in an emission spectrum.

Emission Spectrum for a Hydrogen Atom Lyman series: Balmer series: Paschen series: e falls to 1st energy level e falls to 2nd energy level e falls to 3rd energy level typical emission spectrum H discharge tube, with power supply and spectroscope

1 ST E.L. 2 ND E.L. 3 RD E.L. 4 TH E.L. 5 TH E.L. 6 TH E.L. Lyman (UV) Paschen (IR) Balmer (visible) ~ ~~~ ~~

electromagnetic radiation (i.e., light) -- E B waves of oscillating electric (E) and magnetic (B) fields source is vibrating electric charges

Characteristics of a Wave frequency: the number of cycles per unit time (usually sec) amplitude A crest wavelength trough -- unit is Hz, or s 1 or 1/s

radio waves IR visible UV X-rays gamma rays cosmic rays electromagnetic spectrum: contains all of the types of light that vary according to frequency and wavelength ROYGBVROYGBV large low f low energy small high f high energy -- visible spectrum ranges from only ~400 to 750 nm (a very narrow band of spectrum) microwaves 400 nm750 nm

Albert Michelson (1879) -- first to get an accurate value for speed of light The speed of light in a vacuum (and in air) is constant: c = 3.00 x 10 8 m/s c = f -- Equation: Albert Michelson (18521931)

E = h f In 1900, Max Planck assumed that energy can be absorbed or released only in certain discrete amounts, which he called quanta. Later, Albert Einstein dubbed a light particle that carried a quantum of energy a photon. -- Equation: E = energy, h = Plancks constant in J = 6.63 x 10 34 Js (i.e., J/Hz) Max Planck (18581947) Albert Einstein (18791955)

A radio station transmits at 95.5 MHz (FM 95.5). Calculate the wavelength of this light and the energy of one of its photons. c = f = 3.14 m E = h f= 6.63 x 10 34 J/Hz (95.5 x 10 6 Hz) = 6.33 x 10 26 J 3.00 x 10 8 m/s = 95.5 x 10 6 Hz

Electron Cloud Model Orbital (electron cloud) instead of orbits Region in space where there is 90% probability of finding an electron Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Orbital 90% probability of finding the electron Orbital Shape

Shapes of s, p, and d orbitals

p-Orbitals Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 335 pxpx pypy pzpz

s, p, and d-orbitals s orbitals: Each holds 2 electrons (outer orbitals of Groups 1 and 2) p orbitals: Each of 3 sets holds 2 electrons = 6 electrons (outer orbitals of Groups 3 to 8) d orbitals: Each of 5 sets holds 2 electrons = 10 electrons (found in elements in third period and higher) Kelter, Carr, Scott,, Chemistry: A World of Choices 1999, page 82

f orbitals

Relative Sizes 1s and 2s 1s 2s Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 334

s block p block d block f block 6767 Periodic Patterns 1s1s1s1s 2s2s2s2s 3s3s3s3s 4s4s4s4s 5s5s5s5s 6s6s6s6s 7s7s7s7s 3d3d3d3d 4d4d4d4d 5d5d5d5d 6d6d6d6d 1s1s1s1s 2p2p2p2p 3p3p3p3p 4p4p4p4p 5p5p5p5p 6p6p6p6p 7p7p7p7p 4f4f4f4f 5f5f5f5f 12345671234567 (n-1) (n-2) n

Sections of Periodic Table to Know f-block s-block d-block p-block

Energy Level Diagram of a Many-Electron Atom Arbitrary Energy Scale 18 32 8 8 2 1s 2s 2p 3s 3p 4s 4p 3d 5s 5p 4d 6s 6p 5d 4f NUCLEUS OConnor, Davis, MacNab, McClellan, CHEMISTRY Experiments and Principles 1982, page 177 Each orbital can only hold 2 e- Start from the bottom and add e-

You dont have to memorize the orderjust start at the beginning and fill in e-

s-block1st Period (row) 1s 1 1 e- in 1s orbital Periodic Patterns Example - Hydrogen Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Writing Electron Configurations: Where are the e ? (probably) As H He N Al Li Ti Xe 1s 2 2s 2 3p 6 2p 6 4s 2 3d 10 3s 2 4p 6 1s 1 1s 2 1s 2 2s 1 1s 2 2s 2 2p 3 1s 2 2s 2 3p 1 2p 6 3s 2 1s 2 2s 2 3p 6 2p 6 4s 2 3d 2 3s 2 1s 2 2s 2 3p 6 2p 6 4s 2 3d 10 3s 2 4p 3 1s 2 2s 2 3p 6 2p 6 4s 2 3d 10 3s 2 4p 6 5s 2 4d 10 5p 6 Filling Order

[Ar]4s 2 3d 10 4p 2 Periodic Patterns GermaniumExample - Germanium Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Ge 72.61 32

Electron Configuration Battleship (your shots)

Electron Configuration Battleship (your ships and opponents shots)

S Shorthand Electron Configuration (S.E.C.) To write S.E.C. for an element: 1. Put symbol of noble gas that precedes element in brackets. 2. Continue writing e config. from that point Co In Cl Rb [ Ne ] 3s 2 3p 4 [ Ar ] 4s 2 3d 7 [ Kr ] 5s 2 4d 10 5p 1 [ Ne ] 3s 2 3p 5 [ Kr ] 5s 1 Ge 72.61 32

[ ] neon's electron configuration (1s 2 2s 2 2p 6 ) Shorthand Configuration [Ne] 3s 1 3rd energy level (or 3 rd period) 1 electron in the s orbital orbital shape (s,p,d,fetc.) 1s 2 2s 2 2p 6 3s 1 electron configuration A B C D Na = [Ne]

Shorthand Configuration Review [Ar] 4s 2 Electron configurationElement symbol [Ar] 4s 2 3d 3 [Rn] 7s 2 5f 14 6d 4 [He] 2s 2 2p 5 [Kr] 5s 2 4d 9 [Kr] 5s 2 4d 10 5p 5 [Kr] 5s 2 4d 10 5p 6 or [Xe] [He] 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 Ca V Sg F Ag I Xe Fe [Ar] 4s 2 3d 6

Periodic Patterns Review Period # (1-7) primary energy level (n) (subtract for d & f) Group # (1-8excluding d block) total # of valence e - Column within Sublevel block # of e - in sublevel Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Three Principles about Electrons Aufbau Principle: for equal-energy orbitals (p, d) each must have one e before any take a second Pauli Exclusion Principle: e will fill the lowest-energy orbital available Hunds Rule: two e in same orbital have different spins 1s 2 2s 2 3p 6 2p 6 4s 2 3d 10 3s 2 Friedrich Hund Wolfgang Pauli

General Rules Aufbau Principle Electrons fill the lowest energy orbitals first. Lazy Tenant Rule Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem 2s2s 3s3s 4s4s 5s5s 6s6s 7s7s 1s1s 2p2p 3p3p 4p4p 5p5p 6p6p 3d3d 4d4d 5d5d 6d6d 4f4f 5f5f 1s1s 2s2s 2p2p 3s3s 3p3p 4s4s 4p4p 3d3d 4d4d 5s5s 5p5p 6s6s 7s7s 6p6p 6d6d 4f4f 5f5f 5d5d Energy NO ELEVATOR!

General Rules Hunds RuleHunds Rule Within a sublevel, place one electron per orbital before pairing them. Empty Bus Seat Rule Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem 2p OR

General Rules Pauli Exclusion PrinciplePauli Exclusion Principle Each orbital can only hold TWO electrons and the must have opposite spins. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Wolfgang Pauli 1s

O Orbital Diagrams show spins of e and orbital location 1s 2s 2p3s 3p 1s 2s 2p3s 3p P 1s 2 2s 2 2p 4 1s 2 2s 2 2p 6 3s 2 3p 3

HAVE MORE ENERGY ARE FURTHER FROM NUCLEUS AND The Importance of Electrons orbitals: In a generic e config (e.g., 1s 2 2s 2 2p 6 3s 2 3p 6 ): regions of space where an e may be found # of energy level # of e in those orbitals coefficient superscript In general, as energy level # increases, e

Shorthand Configuration S 16e - Valence Electrons (Highest energy level) Kernel (Core) Electrons S16e - [Ne] 3s 2 3p 4 1s 2 2s 2 2p 6 3s 2 3p 4 Electron Configuration Longhand Configuration Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem S 32.066 16

INVOLVED IN CHEMICAL BONDING kernel (core) electrons: valence electrons: in inner energy level(s); close to nucleus in outer energy level He: Ne: Ar: Kr: 1s 2 [ He ] 2s 2 2p 6 [ Ne ] 3s 2 3p 6 [ Ar ] 4s 2 3d 10 4p 6 Noble gas atoms have FULL valence orbitals. They are stable, low-energy, and unreactive. (2 valence e ) (8 valence e )

octet rule: the tendency for atoms to fill valence orbitals completely with 8 e (outer E level) Other atoms want to be like noble gas atoms doesnt apply to He, Li, Be, B (which require 2) or to H (which requires either 0 or 2)duet rule fluorine atom, F 9 p +, 9 e ** So, they lose or gain e ... gain 1 e or lose 7 e - ? 9 p +, 10 e F is more stable as an F ion FF chlorine atom, Cl 17 p +, 17 e 17 p +, 18 e Cl is more stable as a Cl ion Cl How to be like a noble gas? [He] 2s 2 2p 5 [Ne] 3s 2 3p 5 gain 1 e or lose 7 e - ?

lithium atom, Li 3 p +, 3 e lose 1 e or gain 7 e - ? 3 p +, 2 e Li is more stable as the Li + ion. Li + sodium atom, Na 11 p +, 11 e lose 1 e or gain 7 e - ? 11 p +, 10 e Na is more stable as Na + ion Na + How to be like a noble gas? [He] 2s 1 [Ne] 3s 1

1+ Know charges on these columns of Table: Group 1: Group 2: Group 3: Group 5: Group 6: Group 7: Group 8: 2+ 3+ 3 2 1 0 1+ 2+ 3+ 3 2 1 0

s p d f 6767 Periodic Patterns and Charge Trends 1s1s1s1s 12345671234567 +1 +2 (n-2) n +3 - 3 - 2 - 1 Variable Charge

Naming Ions e.g., Ca 2+ Cs 1+ Al 3+ Cations use element name and then say ion e.g., S 2 P 3 N 3 O 2 Cl 1 Anions change ending of element name to ide and then say ion calcium ion cesium ion aluminum ion sulfide ion phosphide ion nitride ion oxide ion chloride ion

Extra Slides

O 8e - Orbital Diagram Electron Configuration 1s 2 1s 2 2s 2 2s 2 2p 4 Notation 1s 2s 2p Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem O 15.9994 8

unit 3: atomic structure chemistry basics of the atom subatomic particle charge location in the atom...

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