Nucleus: Z = # protons = 1 for hydrogen to 94 for plutonium N = # neutrons Atomic mass A ≈ Z + N...
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Transcript of Nucleus: Z = # protons = 1 for hydrogen to 94 for plutonium N = # neutrons Atomic mass A ≈ Z + N...
Nucleus: Z = # protons
orbital electrons: n = principal quantum number
n=3 2 1
= 1 for hydrogen to 94 for plutoniumN = # neutrons
Atomic mass A ≈ Z + N
BOHR ATOM
CHAPTER 2:ATOMIC STRUCTURE AND INTERATOMIC BONDING
WAVE-MECHANICAL ATOM
• have discrete energy states• tend to occupy lowest available energy state.
Incr
easin
g en
ergy
n=1n=2
n=3
n=4
1s2s
3s2p3p
4s4p 3d
Electrons...ELECTRON ENERGY STATES
Electron Configuration
• Columns: Similar Valence Structure
Electropositive elements:Readily give up electronsto become + ions.
Electronegative elements:Readily acquire electronsto become - ions.
He Ne Ar Kr Xe Rn
iner
t gas
es
acce
pt 1
e ac
cept
2e
give
up 1
e gi
ve u
p 2e
give
up 3
e
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
THE PERIODIC TABLE
Na (metal) unstable
Cl (nonmetal) unstable
electron
+ - Coulombic Attraction
Na (cation) stable
Cl (anion) stable
• Example: NaCl
IONIC BONDING
• Predominant bonding in Ceramics
Give up electrons Acquire electrons
He -
Ne -
Ar -
Kr -
Xe -
Rn -
F 4.0Cl 3.0Br 2.8
I 2.5At 2.2
Li 1.0Na 0.9K
0.8Rb 0.8Cs 0.7Fr 0.7
H 2.1
Be 1.5Mg 1.2Ca 1.0Sr 1.0Ba 0.9Ra 0.9
Ti 1.5
Cr 1.6
Fe 1.8
Ni 1.8
Zn 1.8
As 2.0
CsCl
MgOCaF2
NaCl
O 3.5
EXAMPLES: IONIC BONDING
• Example: CH4
C: has 4 valence e, needs 4 moreH: has 1 valence e, needs 1 moreElectronegativities are comparable.
COVALENT BONDING
shared electrons from carbon atom
shared electrons from hydrogen atoms
H
H
H
H
C
CH4
• Molecules with nonmetals• Molecules with metals and nonmetals• Elemental solids (RHS of Periodic Table)• Compound solids (about column IVA)
He -
Ne -
Ar -
Kr -
Xe -
Rn -
F 4.0Cl 3.0Br 2.8
I 2.5At 2.2
Li 1.0Na 0.9K
0.8Rb 0.8Cs 0.7Fr 0.7
H 2.1
Be 1.5Mg 1.2Ca 1.0Sr 1.0Ba 0.9Ra 0.9
Ti 1.5
Cr 1.6
Fe 1.8
Ni 1.8
Zn 1.8
As 2.0
SiCC(diamond)
H2O
C 2.5
H2
Cl2
F2
Si 1.8
Ga 1.6
GaAs
Ge 1.8
O 2.0
colu
mn
IVA
Sn 1.8Pb 1.8
EXAMPLES: COVALENT BONDING
• Primary bond for metals and their alloys
+ + +
+ + +
+ + +
METALLIC BONDING
• Fluctuating dipoles
HH HHH2 H2
secondary bonding
ex: liquid H2asymmetric electron clouds
+ - + -secondary bonding
SECONDARY BONDING
Ceramics (Covalent & Ionic bonding):
Metals(Metallic bonding):
Polymers(Covalent & Secondary):
secondary bonding
Large bond energylarge Tmlarge Esmall
Variable bond energymoderate Tmmoderate Emoderate
Directional PropertiesSecondary bonding dominates
small Tsmall Elarge
SUMMARY: PRIMARY BONDS