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Atomic Structure Neutrons: neutral Protons: positive charge (1.6x10 - - PowerPoint PPT Presentation

Dec 20, 2023 293 likes •486 views

Kasetsart University 213211: Atomic Structure & Bonding Atomic Structure Neutrons: neutral Protons: positive charge (1.6x10 -19 C, 1.67x10 -27 kg) Electrons: negative charge (-1.6x10 -19 C, 9.11x10 -31 kg) Atomic weight = m

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SLIDE 1

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

6

Atomic Structure

  • Neutrons: neutral
  • Protons: positive charge (1.6x10-19C, 1.67x10-27kg)
  • Electrons: negative charge (-1.6x10-19C, 9.11x10-31kg)
  • Atomic weight = mprotons + mneutrons
  • Atomic number (Z) = # of protons
  • Isotope corresponds to # of neutrons

1 mole = 6.023x1023 atoms (Avogadro’s number)

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SLIDE 2

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

7

Quantum Mechanic: Bohr Atom

  • rbital electrons:

n = principal quantum number n=3 2 1

Nucleus: Z = # protons N = # neutrons = 1 for hydrogen to 94 for plutonium

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SLIDE 3

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

8

Quantum Mechanic: Wave Mechanics

  • Quantum Numbers

– Principle quantum number

n = K, L, M, N, O, …

– Subsidiary quantum number or Subshell

l = s, p, d, f

– Magnetic quantum number or Energy States

ml = 1, 3, 5, 7

– Electron spin quantum number or Spin Moment

ms = +½, -½

Structure of an atom = Electron Configuration Electrons occupy the outermost filled shell = Valence Electrons

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SLIDE 4

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

9

Electron Energy States

  • Electrons

– have discrete energy states – tend to occupy lowest available energy state

Increasing energy n=1 n=2 n=3 n=4 1s 2s 3s 2p 3p 4s 4p 3d

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SLIDE 5

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

10

Expected Electron Configurations

Electron configuration 1s1 1s2

(stable)

1s22s1 1s22s2 1s22s22p1 1s22s22p2 ... 1s22s22p6

(stable)

1s22s22p63s1 1s22s22p63s2 1s22s22p63s23p1 ... 1s22s22p63s23p6

(stable)

... 1s22s22p63s23p63d104s246

(stable)

Element Hydrogen Helium Lithium Beryllium Boron Carbon ... Neon Sodium Magnesium Aluminum ... Argon ... Krypton Atomic # 1 2 3 4 5 6 10 11 12 13 18 ... 36

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SLIDE 6

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

11

The Periodic Table

He Ne Ar Kr Xe Rn

inert gases accept 1e accept 2e give up 1e give up 2e give up 3e

F Li Be Metal Nonmetal Intermediate H Na Cl Br I At O S Mg Ca Sr Ba Ra K Rb Cs Fr Sc Y Se Te Po

Electropositive elements: Readily give up electrons to become + ions. Electronegative elements: Readily acquire electrons to become - ions.

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SLIDE 7

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

12

Bonding Forces and Energies

∫

= dr F E

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SLIDE 8

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

13

Type of Bonding

  • Primary or Chemical Bonds

– Ionic Bonding – Covalent Bonding – Metallic Bonding

  • Secondary or Physical (van der Waals) Bonds

– Fluctuating induced dipole bonds – Polar molecule induced dipole bonds – Permanent dipole bonds

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SLIDE 9

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

14

Chemical Bonds: Ionic Bonding

  • Occurs between + and – ions
  • Requires electron transfer
  • Large different electronegativity required
  • Example: NaCl

Na (metal) unstable Cl (nonmetal) unstable electron

+

  • Coulombic

Attraction Na (cation) stable Cl (anion) stable

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SLIDE 10

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

15

He

  • Ne
  • Ar
  • Kr
  • Xe
  • Rn
  • F

4.0 Cl 3.0 Br 2.8 I 2.5 At 2.2 Li 1.0 Na 0.9 K 0.8 Rb 0.8 Cs 0.7 Fr 0.7 H 2.1 Be 1.5 Mg 1.2 Ca 1.0 Sr 1.0 Ba 0.9 Ra 0.9 Ti 1.5 Cr 1.6 Fe 1.8 Ni 1.8 Zn 1.8 As 2.0

CsCl MgO CaF2 NaCl

O 3.5

Give up electrons Acquire electrons

  • Predominant bonding in Ceramics

Chemical Bonds: Ionic Bonding (con.)

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SLIDE 11

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

16

Chemical Bonds: Covalent Bonding

  • Requires share electrons
  • Directional bond
  • Example: CH4

– C has 4 valence eˉ, needs 4 more – H has 1 valence eˉ, needs 1 more

  • Electronegativities are

comparable

shared electrons from carbon atom shared electrons from hydrogen atoms H H H H C

CH4

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SLIDE 12

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

17

Chemical Bonds: Covalent Bonding (con.)

He

  • Ne
  • Ar
  • Kr
  • Xe
  • Rn
  • F

4.0 Cl 3.0 Br 2.8 I 2.5 At 2.2 Li 1.0 Na 0.9 K 0.8 Rb 0.8 Cs 0.7 Fr 0.7 H 2.1 Be 1.5 Mg 1.2 Ca 1.0 Sr 1.0 Ba 0.9 Ra 0.9 Ti 1.5 Cr 1.6 Fe 1.8 Ni 1.8 Zn 1.8 As 2.0

SiC C(diamond) H2O

C 2.5

H2 Cl2 F2

Si 1.8 Ga 1.6

GaAs

Ge 1.8 O 2.0

column IVA

Sn 1.8 Pb 1.8

  • Molecule with nonmetals
  • Molecule with metals and nonmetals
  • Compound solids (about column IVA)
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SLIDE 13

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

18

Chemical Bonds: Metallic Bonding

  • Arises from a sea of donated valence electrons

(1, 2, or 3 from each atom)

  • Nondirectional bond
  • Primary bond for metals and their alloys

+ + + + + + + + +

Ion cores Sea of valence electrons

  • r electron cloud
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SLIDE 14

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

19

Physical or van der Waals Bonds

  • Arises from atomic or molecular dipoles.
  • Weak in comparison to the primary bonds.
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SLIDE 15

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

20

Physical Bonds: Fluctuating dipoles

asymmetric electron clouds

+

  • +
  • secondary

bonding

H H H H H2 H2

secondary bonding

ex: liquid H2

An electrically symmetric atom An induced atomic dipole Inert gases and electrically neutral and symmetric molecules, ex. H2, Cl2 Weakest bonds

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SLIDE 16

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

21

Physical Bonds: Polar Molecule

  • Can induce dipoles in adjacent

nonpolar molecules.

  • Bond forms between the two

molecules, which the magnitude is greater than for fluctuating induced dipoles.

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SLIDE 17

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

22

Physical Bonds: Permanent dipoles

  • Exist between adjacent polar molecules.
  • Energy are greater than induced dipoles.
  • Ex: Hydrogen bonding: H – F, H – O, or H – N bond

Hydrogen Fluoride

secondary bonding

Polymer

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SLIDE 18

Kasetsart University

Dr.Peerapong Triyacharoen Department of Materials Engineering

213211: Atomic Structure & Bonding

23

Summary

Directional (inter-molecular, inter- chain polymer) Smallest Secondary Nondirectional (metals) Variable large – Tungsten small – Mercury Metallic Directional (semiconductor, ceramics, polymer chains) Variable large – Diamond small – Bismuth Covalent Nondirectional (ceramics) Large Ionic Comment Bond Energy Type