Learning Objectives. Decreasing size. ~10 3 m. ~10 6 m. ~10 10 m 1/22/2013. Describe ionic, covalent, and metallic, hydrogen, and van der Waals bonds.

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1 Lectue #0 Chapte Atomic Bonding Leaning Objectives Descibe ionic, covalent, and metallic, hydogen, and van de Waals bonds. Which mateials exhibit each of these bonding types? What is coulombic foce of epulsion and coulombic foce of attaction and how to calculate both. 1 It all stats with atoms Deceasing size..powes of ten ~10 3 m ~10 6 m ~10 10 m 1

2 Atoms Bond Atoms ae the smallest unit of matte that etains the identity of the substance Atoms self assemble in diffeent ways to build up the stuctue of a mateial. What do we lean in this image? 3 Boh Model of the atom Kind of like the sola system The 3 d ing can hold up to 18 e - The 4 th ing and any afte can hold up to 3 e - Nucleus consists of potons and neutons The 1 st ing can hold up to e - The nd ing can hold up to 8 e - Electons have ( ) chage little mass (~10 9 g) 4 IN the NUCLEUS Potons have (+) chage Neutons have 0 chage Same mass depends on atom type (~10 7 g) 1

3 Boh Model of the atom Obitals/Shells The 3 d ing can hold up to 18 e - The 4 th ing and any afte can hold up to 3 e - K L M N Nucleus consists of potons and neutons The 1 st ing can hold up to e - The nd ing can hold up to 8 e - Electons have ( ) chage little mass (~10 9 g) 5 IN the NUCLEUS Potons have (+) chage Neutons have 0 chage Same mass depends on atom type (~10 7 g) Boh Atom vs. Obital Desciption z x Vesus y s Obital Obitals adopt cetain configuations Enegy p 3s 3p 3d 4s 4p Futhe fom the nucleus (highe enegy state) 6 1s s Filling of shells is based on obital type 3

4 # potons = # electons (+1) (-1) If 0 potons ae pesent in an atom then 0 electons ae thee to balance the oveall chage of the atom atoms ae neutal. The neutons have no chage; theefoe they do not have to equal the # potons o # electons. 4 7 How do we know the numbe of subatomic paticles in an atom? Atomic numbe: this numbe indicates the numbe of potons in an atom. Ex: Hydogen s atomic numbe is 1. # potons? So hydogen has 1 poton Ex: Cabon s atomic numbe is 6. # potons? So cabon has 6 potons **The numbe of potons identifies the atom. 6 4

5 9 Check out It s vey cool! Oute Shells have 1 electon How to ead and use a Peiodic Table Inceasing # of electons (potons) Oute Shells missing electons Oute Shells missing 1 electon All Shells filled (noble) 10 Atomic # = # of potons (o electons) Atomic Mass Unit (amu): 1 amu = 1.66 x 10 7 kg (based on the unit of mass of 1/1 of 1 C) g Cu Atomic mass of Cu = amu o Avogado s numbe (6.0 x 3 mol 1 ) 5

6 Atoms want to fill (complete) thei shells esults in electonic (electon) tansfe o bonding with each othe, ex. H BONDING K L M N 4p Enegy 3p 3d 4s 3s p s 1s 11 1 Pimay Atomic Bonds Covalent: Shaed oute shell electons. Diectional Ionic: Donation of valence electon (e ) to balance chage. Metallic: Sea of electons. Nondiectional. Hydogen: Attaction between H + to adjacent molecule () van de Waals: Attaction between (+) and () chaged egions. 5 6

7 Bond Bond Stength (GPa) Example of Bond Covalent 1,000 Diamond Ionic Salt and Ceamics Metallic Metals Hydogen 8 Ice Van de Waals Polymes Stongest Weakest Bond type influences stuctue and popeties! 13 The Ionic Bond Ionic bonding between sodium (Na) and chloine (Cl) atoms. Electon Tansfe (donation) Electon tansfe fom Na to Cl ceates a cation (Na + ) and an anion (Cl ). The ionic bond is due to the coulombic attaction between ions of opposite chage. Ionic Bonds ae non-diectional Na Ionic Bond Cl Na + Cl - Cation (Na + ) becomes smalle than the neutal Na atom. 14 Anion (Cl ) becomes lage than the Cl neutal atom. 7

8 Oute shell has only one electon Oute shell missing one electon Electon donation makes both ions happy 15 Fomation of an ionic bond between sodium and chloine in which the effect of ionization on atomic adius is illustated. The cation (Na + ) becomes smalle than the neutal atom (Na), while the anion (Cl ) becomes lage than the neutal atom (Cl). 16 Li + Yet anothe example of the ionic bond Fl 3+ Lithium atom Li 3+ Electon Tansfe (donation) Fluoine atom F Figue Schematic illustation of ionic bonding between lithium and fluoine. As befoe, the effect of ionization on atomic adius is illustated. The cation (Li + ) becomes smalle than the neutal atom (Li), while the anion (F ) becomes lage than the neutal atom (F). Lithium ion Li + Fluoine atom F - 8

9 IONIC BONDING & STRUCTURE Chage Neutality: --Net chage in the stuctue should CaF: Ca + + cation be zeo. --Geneal fom: F - anions F - AmXp m, p detemined by chage neutality Stable stuctues: --maximize the # of neaest oppositely chaged neighbos. 17 Na + Cl - Net bonding foce cuve fo a Na + Cl pai showing an equilibium bond length of o = 0.8 nm. o Same as cuve as befoe F A (coulombic foce of attaction) F N (net bonding foce) Foce 0 This cuve is the diffeence between the attactive and epulsive cuves (F N = F A + F R ) F R (coulombic foce of epulsion) Repulsive b/c of ovelapping electic fields 18 Simila to Figue.8(a) fom text 9

10 Bonding distance is a balanced distance The bonding enegy, E, is elated to the bonding foce, F, though: Na + Cl - P. 7 de E Fd F d Equilibium bond length (a o ) occus whee F = 0 and E is a minimum Foce bonding foce = 0 Extenally applied compessive foce is equied to push ions close + togethe than o. 0 Extenally applied tensile foce is equied to pull ions futhe apat E 0 than o. Mechanical behavio depends on minimum bonding enegy bonding! See Chap. 7! Figue.8 fom text 19 Note these geneal cuve shapes applied to othe bonding types too gy Ene Coulombic foce fo a Na + Cl pai. F A de A d Na + Cl - Attactive foce between two opposite chages P. 9 e = single electon chage (1.60x10 19 C) Popotionality constant (9x10 9 V/C) A A ( Z e)( Z e) 0 1 Z= valence of the chaged ion, i.e. +1 fo Na + and 1 fo Cl (attactive foce) F A Close the chaged species, the geate the attaction, up to a point! Inteatomic sepaation 0 These equations apply to ionic bonds but NOT covalent A o 1 Fom P

11 Regula stacking of Na + and Cl ions in solid NaCl, which is indicative of the non-diectional natue of ionic bonding 1 Cl Na + CLASS ROOM EXAMPLE: So fa, we have concentated on the coulombic foce of attaction between ions. But like ions epel each othe. A neaest-neighbo pai of Na + ions (shown below)ae sepaated by a distance of o, whee o is defined as the distance between Cl and Na + ions. Calculate the coulombic foce of epulsion between such a pai of like ions. 11

12 3 CLASS ROOM EXAMPLE So fa, we have concentated on the coulombic foce of attaction between ions. But like ions epel each othe. A neaest-neighbo pai of Na + ions (shown below)ae sepaated by a distance of o, whee o is defined as the distance between Cl and Na + ions. Calculate the coulombic foce of epulsion between such a pai of like ions. Given: 9 o 0.8 nm m o (See the next page) At equilibium: Ao 1 Fo like atoms, ( Z e )( Z e F ) A FR 9 whee Ao 9 10 V m/ C ; Z1, Z valence ; 18 e C (9 10 V m/ C)( 1)( C)( 1)( C) 9 (1 V C / m 1 N) FR ( m) 9 N To solve this poblem you need to teat o as the distance between adjacent Na 1+ and Cl 1 ions. Just some simple geomety Use geomety to detemine the distance between adjacent Na 1+ ions o adjacent Cl 1 ions. This is shown below. This new inteatomic t i distance () will be the one that you substitute into the equation fo coulombic foce. In this poblem o Na 1 Cl 1 o o 4 Fom geomety, you can see that: o o o 0.8 nm fo this poblem. 1 1 Na Cl 1

13 CLASS ROOM EXAMPLE Calculate the coulombic foce of attaction between Ca + and O - in CaO, which has the NaCl-type stuctue. 5 CLASS ROOM EXAMPLE SOLUTION Calculate the coulombic foce of attaction between Ca + and O - in CaO, which has the NaCl-type stuctue. Fom font cove of text: Ionic Radii fo Ca and O nm m Ca nm m O Inteatomic Sepaation: ao ( m) ( m) m Ca O F R (9 10 V m/ C)( )(0.16 )( C )( )(016 )( C) 9 ( m) N 6 13

14 Summay Thee ae five types of atomic bonds: Covalent, Ionic, Metallic, Hydogen, and Van de Waals. The bond type influences the stuctue and popeties of a mateial. Coulombic foce of epulsion and coulombic foce of attaction can be calculated using A The equation elating coulombic foce of epulsion and coulombic foce of attaction is: F A =-F R F A 7 14

1240 ev nm 2.5 ev. (4) r 2 or mv 2 = ke2

1240 ev nm 2.5 ev. (4) r 2 or mv 2 = ke2 Chapte 5 Example The helium atom has 2 electonic enegy levels: E 3p = 23.1 ev and E 2s = 20.6 ev whee the gound state is E = 0. If an electon makes a tansition fom 3p to 2s, what is the wavelength of the