CHAPTER 2 Structure of Solid Dr. Syafiqah Saidin CHAPTER 2 Structure of Solid SMBE3313 2017/2018 Semester 1

Bonding Energy / Potential Energy Dr. Syafiqah Saidin OUTLINE Introduction to Solid Atomic Structure Bonding Energy / Potential Energy Ionic Bonding Covalent Bonding Metallic Bonding Secondary Bonding

Introduction to Solid Solid Dr. Syafiqah Saidin Introduction to Solid Solid State of matter with its constituent atoms held together by strong interatomic forces Interatomic forces Ionic bonding Covalent bonding Metallic bonding Primary Strong interatomic force

Atomic Structure Atom : Electron = 9.11 x 10-31 kg Proton Neutron Dr. Syafiqah Saidin Electron (ē) Atom : Electron = 9.11 x 10-31 kg Proton Neutron Atomic number = No of protons in nucleus of atom / No of electrons of neutral species Atomic mass (A) = N + Z Neutron (N) 1.67 x 10-27 kg Proton (Z) Atomic mass unit (amu) = 1/12 mass of carbon, C-12 Molecular weight/molar mass (g/mol) = Weight of atomic particles 1 amu/atom = 1 g/mol C has been set as the standard international reference • Bohr Atomic Model: Electrons are assumed to revolve around the atomic nucleus in discrete orbitals •Describe electrons in atoms in terms of both position (electron orbitals) and energy

Electron at the outermost orbital Atomic Structure Dr. Syafiqah Saidin X A Atomic mass Isobar : Same A, different Z Isotope : Same Z, different N Isotone : Same N Element Z No of protons Electron (ē) Neutron (N) Valence electron Electron at the outermost orbital Orbital Proton (Z) Bohr atom model

Atomic Structure Electron energy state Dr. Syafiqah Saidin Atomic Structure Electron energy state Occupy the atomic no. at the lowest energy state to higher energy state Low K shell L shell M shell N shell n= principal quantum no; shell or energy level l= orbital momentum quantum no; subshell of electron; s=0; p=1; d=2; f=3 so forth Ml= magnetic quantum no; orbital of a given subshell; -l<x<+l Ms= spin magnetic quantum no; +1/2 / -1/2 Aufbau principle: 1s<2s<2p … Madelung rule: dalam figure No. of electron can occupy each orbital: s = 2; p = 6; d = 10; f = 14 High

Atomic Structure Ex: Electron energy state of several elements Dr. Syafiqah Saidin Ex: Electron energy state of several elements http://www.sparknotes.com/chemistry/fundamentals/atomicstructure/section2.rhtml

Atomic Structure Exercise Dr. Syafiqah Saidin Exercise Write the electron energy state for the following elements: Sodium, Na Magnesium, Mg Titanium, Ti Fluorine, F Chlorine, Cl Na, 11=1s2 2s2 2p4 3s2 3p1; valence=3 Mg, 12=1s2 2s2 2p4 3s2 3p2; valence=4 Ti, 22=1s2 2s2 2p4 3s2 3p2 4s2 3d8; valence=12 F, 9=1s2 2s2 2p4 3s1; valence=1 Cl, 17

Periodic Table Inert gas Give 1ē Give 2ē Receive 2ē Receive 1ē Dr. Syafiqah Saidin Inert gas Give 1ē Give 2ē Receive 2ē Receive 1ē http://www.ptable.com/

Periodic Table Electronegativity: Ranges from 0.7 to 4.0 Dr. Syafiqah Saidin Electronegativity: Ranges from 0.7 to 4.0 Higher electronegativity – Higher tendency to receive electrons Increase electronegativity http://www.ptable.com/

Bonding Energy / Potential Energy Dr. Syafiqah Saidin Bonding Energy / Potential Energy When two atoms are close, both of them are under the influence of two forces: Attractive force – The force that attract both atoms to be closed Repulsive force - The force by the positive charges that push away one atom to another https://saylordotorg.github.io/text_general-chemistry-principles-patterns-and-applications-v1.0/s12-05-lewis-structures-and-covalent-.html

Bonding Energy / Potential Energy Dr. Syafiqah Saidin Bonding Energy / Potential Energy Net energy, EN = Repulsive energy, ER + Attractive energy, EA Repulsive force : Dominates at small distance Attractive force : Dominates at larger distance At equilibrium : Both are equal Low energy : The element is more stable https://nirajchawake.wordpress.com/2014/08/11/derivation-of-hookes-law/

Bonding Energy / Potential Energy Dr. Syafiqah Saidin Bonding Energy / Potential Energy Tm : Melting temperature Eo : Elastic modulus / Young’s modulus Relation between bonding energy and melting temperature Relation between bonding energy and elastic modulus http://web.eng.fiu.edu/wangc/EGN3365-2b

Bonding Energy / Potential Energy Dr. Syafiqah Saidin Bonding Energy / Potential Energy Force Deformed metal + + Force High attraction force, low repulsive force Low attraction force, high repulsive force http://web.eng.fiu.edu/wangc/EGN3365-2b

Bonding Energy / Potential Energy Dr. Syafiqah Saidin Bonding Energy / Potential Energy Relation between bonding energy and melting temperature Bonding Type Substance Bonding energy (kJ/mol) Melting temperature Ionic NaCl 640 801 MgO 1000 2800 Covalent Si 450 1410 Diamond 713 >3550 Metallic Al 324 660 Fe 406 1538 Van der Waals Ar 7.7 -189 Cl2 31 -101 Bonding energy Melting temperature http://web.eng.fiu.edu/wangc/EGN3365-2b

Ionic Bonding Metallic compound Non-metallic compound Donate electron Dr. Syafiqah Saidin Metallic compound Donate electron Non-metallic compound Accept electron ē Transferring free valence electron to be stable Metallic Mg Cl + - Cation Anion Electrostatic force / Coulomb effect Ex : Mg+ ion Ex : Cl- ion

Dr. Syafiqah Saidin Ionic Bonding In solid state, cations are occupied/surrounded by as many anions to reduce repulsion force between cations, thus leading to solid arrangement of a crystal structure Ionic solid is a poor electrical conductor since electrons are no longer carry charge (have difficulties in carry charge) due to tight molecule arrangement. Ex: NaCl, MgO, AgCl, etc

Ionic Bonding Typical metal crystal structure Dr. Syafiqah Saidin Typical metal crystal structure Au = 3 atoms in each unit cell; Fe = 2 Exercise: Gold (Au) and iron (Fe) have FCC and BCC crystal arrangements, respectively, how many atoms in each unit cell? http://2012books.lardbucket.org/books/principles-of-general-chemistry-v1.0/s16-02-the-arrangement-of-atoms-in-cr.html

Ionic Bonding Exercise Dr. Syafiqah Saidin Exercise 1. Calculate the density of metallic Fe if the edge length of a unit cell is 286.6 pm. Given : Avogadro no. = 6.02 x 1023 atoms/mol Molecular weight = 55.85 g/mol 7.87 g/cm3

Ionic Bonding Exercise Dr. Syafiqah Saidin Exercise 2. The density of nickel is 8.908 g/cm3. If the metallic radius of nickel is 125 pm, what is the structure of metallic nickel? Atomic weight, Ni = 58.69 3. Lithium crystallizes in a bcc structure with an edge length of 3.509 Å. Calculate its density. What is the approximate metallic radius of lithium in picometers? Atomic weight, Li : 6.94 g/mol Fcc d = 0.5335 g/cm3, r =151.9 pm

Ionic Bonding Transfer electron Receive electron Dr. Syafiqah Saidin http://www.ptable.com/

Covalent Bonding Dr. Syafiqah Saidin Mostly involves elements in the middle of periodic table which have tendency to donate and receive electrons Bonding principle: sharing valence electrons Ex: Methane, CH4 C H C has 4 valence electrons to be shared H has 2 valence electrons to be shared

Ex: Diamond, silicon, graphite Covalent Bonding Dr. Syafiqah Saidin In a large group, the atoms often form a tetrahedron arrangement, lead to orderly repeating pattern Localization of valence electrons cause these materials to be poor electrical conductor too Ex: Diamond, silicon, graphite Graphite arrangement Diamond arrangement Diamond : cubic; graphite : hexagonal https://www.mbi-berlin.de/en/research/highlights/highlight_graphite.html

Covalent Bonding Mostly column IVA Dr. Syafiqah Saidin http://www.ptable.com/

Metallic Bonding Dr. Syafiqah Saidin For strong metal electron donor, they are bonded through metallic bonding instead of ionic and covalent bonding Most metals have high melting point due to this strong bonding Metal atoms are arranged in 3D repeating order, closely packed where its valence electrons are floating between atoms like a gas Delocalised electrons + Positive charge metal ions Metallic bonding structure

Dr. Syafiqah Saidin Metallic Bonding Electrical charge are neutralized within the crystal structure where negative charge behaves like a glue between the positive charge core. Metal is possibly be deformed and deployed due to this metallic bonding arrangement Force + + Force Deformed metal

Secondary bonding Van der Waals bonding: Dr. Syafiqah Saidin Secondary bonding Van der Waals bonding: Binding forces between atomic group or molecules other than the ionic, covalent and metallic bonding 3 – 10% weaker than the primary bonding Normally arise between the covalent bonding among molecules and between dipoles It doesn’t have direction Strong attraction between near molecules compared to farther molecules

Covalent bonding Van der Waals bonding Water, H2O Dr. Syafiqah Saidin https://www.boundless.com/biology/textbooks/boundless-biology-textbook/the-chemical-foundation-of-life-2/atoms-isotopes-ions-and-molecules-50/hydrogen-bonding-and-van-der-waals-forces-1001-17178/ https://www.youtube.com/watch?v=Z8oeO1BUyKE

Dr. Syafiqah Saidin https://www.youtube.com/watch?v=X9FbSsO_beg