Chapter 2: Atomic Structure & Interatomic Bonding ISSUES TO ADDRESS... What promotes bonding? What types of bonds are there? What properties are inferred from bonding? Chapter 2 - 1 Atomic Structure (Freshman Chem.) atom electrons 9.11 x 10-31 kg protons 1.67 x 10-27 kg neutrons } atomic number = # of protons in nucleus of atom = # of electrons of neutral species A [=] atomic mass unit = amu = 1/12 mass of 12C
Atomic wt = wt of 6.022 x 1023 molecules or atoms 1 amu/atom = 1g/mol C H 12.011 1.008 etc. Chapter 2 - 2 AVAGADROS NUMBER = 6.022 x 1023 = NA ATOMIC OR MOLECULAR WEIGHT = NA x WEIGHT PER ATOM. number of neutrons = N number of protons = Z A= Z + N (2.1) Chapter 2 - 3 Atomic Structure Valence electrons determine all of the
following properties 1) 2) 3) 4) Chemical Electrical Thermal Optical Chapter 2 - 4 BOHR ATOM Chapter 2 - 5 WAVE MECHANICAL MODEL OF ATOM Chapter 2 - 6
Electronic Structure Electrons have wavelike and particulate properties. This means that electrons are in orbitals defined by a probability. Each orbital at discrete energy level is determined by quantum numbers. Quantum # Designation n = principal (energy level-shell) l = subsidiary (orbitals) ml = magnetic K, L, M, N, O (1, 2, 3, etc.) s, p, d, f (0, 1, 2, 3,, n -1) 1, 3, 5, 7 (-l to +l) ms = spin , -
Chapter 2 - 7 Electron Energy States Electrons... have discrete energy states tend to occupy lowest available energy state. 4d 4p N-shell n = 4 3d 4s Energy 3p 3s M-shell n = 3 Adapted from Fig. 2.4, Callister & Rethwisch 8e.
2p 2s L-shell n = 2 1s K-shell n = 1 Chapter 2 - 8 SURVEY OF ELEMENTS Most elements: Electron configuration not stable. Element Atomic # Hydrogen 1 Helium 2 Lithium 3 Beryllium
1s 2 2s 2 2p 6 3s 1 1s 2 2s 2 2p 6 3s 2 1s 2 2s 2 2p 6 3s 2 3p 1 ... Why? Valence (outer) shell usually not filled completely. Chapter 2 - 9 Electron Configurations Valence electrons those in unfilled shells Filled shells more stable Valence electrons are most available for bonding and tend to control the chemical properties example: C (atomic number = 6) 1s2 2s2 2p2 valence electrons Chapter 2 - 10 Electronic Configurations ex: Fe - atomic # = 26 1s2 2s2 2p6 3s2 3p6
4d 4p 3d 6 4s2 N-shell n = 4 valence electrons 3d 4s Energy 3p 3s M-shell n = 3 Adapted from Fig. 2.4, Callister & Rethwisch 8e. 2p 2s
L-shell n = 2 1s K-shell n = 1 Chapter 2 - 11 give up 1egive up 2egive up 3e- Columns: Similar Valence Structure accept 2eaccept 1einert gases The Periodic Table H He Li Be O
F Ne Na Mg S Cl Ar K Ca Sc Rb Sr Y Cs Ba Se Br Kr Te I Adapted from
Fig. 2.6, Callister & Rethwisch 8e. Xe Po At Rn Fr Ra Electropositive elements: Readily give up electrons to become + ions. Electronegative elements: Readily acquire electrons to become - ions. Chapter 2 - 12 Electronegativity Ranges from 0.7 to 4.0, Large values: tendency to acquire electrons.
Smaller electronegativity Larger electronegativity Adapted from Fig. 2.7, Callister & Rethwisch 8e. (Fig. 2.7 is adapted from Linus Pauling, The Nature of the Chemical Bond, 3rd edition, Copyright 1939 and 1940, 3rd edition. Copyright 1960 by Cornell University. Chapter 2 - 13 Ionic bond metal + donates electrons nonmetal accepts electrons Dissimilar electronegativities ex: MgO
Mg 1s2 2s2 2p6 3s2 [Ne] 3s2 Mg2+ 1s2 2s2 2p6 [Ne] O 1s2 2s2 2p4 O2- 1s2 2s2 2p6 [Ne] Chapter 2 - 14 Electrons in different shells Chapter 2 - 15 Electrons in Sodium and Chlorine
TABLE 2.2 / P 25 3s1 3s2 3p5 Chapter 2 - 16 Ionic Bonding Occurs between + and - ions. Requires electron transfer. Large difference in electronegativity required. Example: NaCl Na (metal) unstable Cl (nonmetal)
unstable electron Na (cation) stable + Coulombic Attraction Cl (anion) stable Chapter 2 - 17 Chapter 2 - 18 FORCES AND ENERGIES Chapter 2 - 19
Chapter 2 - 20 Chapter 2 - 21 Bonding Forces and Energies 2.13 Calculate the force of attraction between a K+ and an O2- ion the centers of which are separated by a distance of r0 =1.5 nm. Solution The attractive force between two ions FA is just the derivative with respect to the interatomic separation of the attractive energy expression, Equation 2.8, which is just Chapter 2 - 22 A d dE A A r
FA = = = 2 dr dr r The constant A in this expression is defined in footnote 3. Since the valences of the K+ and O2- ions (Z1 and Z2) are +1 and -2, respectively, Z1 = 1 and Z2 = 2, then Chapter 2 - 23 FA (Z1e) (Z 2 e) = 2 40r
(1)(2 )(1.602 10 19 C) 2 = (4)() (8.85 10 12 F/m) (1.5 10 9 m) 2 =2.05 10^(-10 ) N Chapter 2 - 24 IONIC FORCE / P 31 FOOT-NOTE F= (Z1 *Z2 * e^2)/(4**0*r^2); e= 1.602 *10^(-19) COULOMBS ; 0 = 8.85 * 10^(-12 ) Z1, Z2 = VALENCIES OF IONS Chapter 2 - 25 Ionic Bonding Energy minimum energy most stable Energy balance of attractive and repulsive terms EN = EA + ER =
A r B rn Repulsive energy ER Interatomic separation r Net energy EN Adapted from Fig. 2.8(b), Callister & Rethwisch 8e. Attractive energy EA Chapter 2 - 26 Examples: Ionic Bonding
Predominant bonding in Ceramics NaCl MgO CaF 2 CsCl Give up electrons Acquire electrons Adapted from Fig. 2.7, Callister & Rethwisch 8e. (Fig. 2.7 is adapted from Linus Pauling, The Nature of the Chemical Bond, 3rd edition, Copyright 1939 and 1940, 3rd edition. Copyright 1960 by Cornell University. Chapter 2 - 27 Covalent Bonding similar electronegativity share electrons bonds determined by valence s & p orbitals dominate bonding Example: CH4 C: has 4 valence e-, needs 4 more
CH 4 H: has 1 valence e-, needs 1 more H Electronegativities are comparable. H C H shared electrons from carbon atom H shared electrons from hydrogen
atoms Adapted from Fig. 2.10, Callister & Rethwisch 8e. Chapter 2 - 28 Primary Bonding Metallic Bond -- delocalized as electron cloud Ionic-Covalent Mixed Bonding (X A X B )2 % ionic character = 4 1 e x (100%)
where XA & XB are Pauling electronegativities Ex: MgO X Mg = 1.2 XO = 3.5 % ionic character 1 e ( 3.5 1.2 )2 4
x (100%) 73.4% ionic Chapter 2 - 29 METALLIC BONDING Chapter 2 - 30 SECONDARY BONDING Arises from interaction between dipoles Fluctuating dipoles asymmetric electron clouds + - + secondary bonding
- ex: liquid H 2 H2 H2 H H H H secondary bonding Adapted from Fig. 2.13, Callister & Rethwisch 8e. Permanent dipoles-molecule induced -general case: -ex: liquid HCl -ex: polymer +
- H Cl secon da secondary bonding + secondary bonding H Cl r y bo n di n g -
Adapted from Fig. 2.15, Callister & Rethwisch 8e. secondary bonding Chapter 2 - 31 Summary: Bonding Comments Type Bond Energy Ionic Large! Nondirectional (ceramics) Covalent Variable
Chapter 2 - 32 Properties From Bonding: Tm Bond length, r Melting Temperature, Tm Energy r Bond energy, Eo ro Energy r smaller Tm unstretched length ro r
Eo = bond energy larger Tm Tm is larger if Eo is larger. Chapter 2 - 33 Properties From Bonding : Coefficient of thermal expansion, length, Lo coeff. thermal expansion unheated, T1 L =(T2 -T1) Lo L heated, T2
~ symmetric at ro Energy unstretched length ro Eo Eo r is larger if Eo is smaller. larger smaller Chapter 2 - 34 Summary: Primary Bonds Ceramics (Ionic & covalent bonding): Metals
large Tm large E small Variable bond energy (Metallic bonding): Polymers (Covalent & Secondary): secon da Large bond energy r y bo n di n g moderate Tm moderate E moderate
Directional Properties Secondary bonding dominates small Tm small E large Chapter 2 - 35 ANNOUNCEMENTS Reading: Core Problems: Self-help Problems: Chapter 2 - 36
Alec Pentland, approaching relationships from a totally different position, supports Stacey with his Social Physics approach. Pentland, an MIT Professor, approached innovation and found that the ... Hay, R., A. (2016), Leading with Limited Knowledge, PhD, University of the West...
Connecting codes/extracts to create themes [Put participants into pairs or smaller groups and give each pair an envelop containing several codes from a data set/code book. Ask participants to work in groups to create code piles using the various codes...
MacroEconomic Goals. Full Employment. That does NOT mean that everybodyhas a job . There is . always. going to be some people unemployed. Civilian Labor Force: People 16 or older who have looked for a job in the past 4...
Forward-Looking Statements. This presentation contains forward-looking statements and forward-looking information within the meaning of applicable securities laws (collectively, "forward-looking statements") including statements concerning anticipated clinical development activities, the potential benefits of product candidates and anticipated market opportunities.
Liz Chappell - In Memoriam . Birmingham Health, Safety & Environment Association . It is with great sadness that we have to report the death of Liz Chappell, wife of Andy Chappell - Secretary of the Association from 1996 to...
Do we need to use PS minus NS measures? (NS=Negative Sentiment) Research literature on Sentiment Analysis (word/doc sentiment assessment software ? Strategy: Each day buy the stock with the greatest Positive Sentiment Tweet Bloom? Why might the positions of words...
DNA replication is semi-conservative DNA polymerase mechanism Examples of eukaryotic DNA polymerases DNA polymerase activities -- 5'-->3' nucleotide addition DNA polymerase reactions -- editing DNA polymerase reactions -- nick translation DNA pol I Klenow fragment lacks 5'-->3' exonuclease Structure of...
Ready to download the document? Go ahead and hit continue!