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Atomic Structure
Guna Selvaduray
MatE 115
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G.
Selvaduray,
SJS
U,
Fall2006
Describe the structure of an atom, including
number of neutrons, protons, electrons,atomic weight and atomic number.
Explain similarities and differences among
Describe ionization potential Identify 1st, 2nd and 3rd ionization potentials
and the relationship to stoichiometry and
nonstoichiometry in compounds. Describe electron affinity
Describe electronegativity
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G.
Selvaduray,
SJS
U,
Fall2006
Structure of the Atom
Atomic Weight
Atomic Number
Number of Protons
Number of Neutrons Number of Electrons
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G.
Selvaduray,
SJS
U,
Fall2006
Quantum Numbers
n: Principal quantum number n= 1, 2, 3,
Corresponding electronic shells: K, L, M, Major determining factor for energy
l: Angular momentum l= 0, 1, 2, , n-1 Corresponds to: s, p, d, f, electrons s electrons (l= 0) have zero angular momentum
They have spherical orbitals p, d, f, .. electrons have directionality to their orbitals
ml: magnetic quantum number -l< ml< +l Specifies orientation of angular momentum in space
ms: spin
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G.
Selvaduray,
SJS
U,
Fall2006
Spin
ms: angular momentum of electron due to
spinning on its own axis ms = + or -
Paulis Exclusion Principle:
No two electrons in a given atom can havethe same set of quantum numbers
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G.
Selvaduray,
SJS
U,
Fall2006
Quantum State
Specified by a unique combination of:
n, m, ml, ms
Orbitals withnucleus as
center
Spin wrtelectronsaxis
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G.
Selvaduray,
SJS
U,
Fall2006
Electronic Structure
SnO, SnO21s22s22p63s23p23d104s24p64d105s25p2Sn
Cu2O, CuO1s2
2s2
2p6
3s2
3p2
3d10
4s1
Cu
FeO, Fe2O31s22s22p63s23p23d64s2Fe
SiO41s22s22p63s23p2Si
Al2O31s22s22p63s23p1Al
MgO1s22s22p63s2Mg
NaO1s22s22p63s1Na
CompoundsElectronic StructureElement
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G.
Selvaduray,
SJS
U,
Fall2006
Atoms, Ions and Isotopes.
Atoms
Features Examples
Ions Features
Examples
Isotopes Features
Examples
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G.
Selvaduray,
SJS
U,
Fall2006
Isotope nomenclature
Types of radiation : helium particles
: electrons
: electromagnetic radiation
U234
92 He
4
2
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G.
Selvaduray,
SJS
U,
Fall2006
Production of Isotopes
Isotopic separation
Target isotope bombarded with (charged)particles
Neutron capture with decay
nIrdOs1
0
192
77
2
1
192
76 2++
++ PdnPd
103
46
1
0
102
46
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G.
Selvaduray,
SJS
U,
Fall2006
Ionization Potential
Energy required to remove an electron
from the atom 1st, 2nd, 3rd, .. Ionization Potential
Relationship of Ionization Potential to: Stoichiometric Compounds, and
Nonstoichiometric Compounds
Units: eV;Sources: W.J. Moore, Physical Chemistry, and L. Pauling,The Nature of the Chemical Bond
0.750.28Cu5.650.670.35Be
2.950.550.28Mg
1.880.440.23Ca
2.621.750.19Na
I3I2I1Element
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G.
Selvaduray,
SJS
U,
Fall2006
Ionization Potential = Ionization Energy
Electron Affinity: Energy given up when an initially free
electron is added to the outer shell of an
atom
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G.
Selvaduray,
SJS
U,
Fall2006
Not to be Confused with
Electropositive elements: Elements which, in their elemental state, nearly
always donate one or more electrons per atom whenthey react chemically to yield stable compounds.
They are electron donors, and their atoms tend to
become positive ions Electronegative elements:
The uncharged atoms of these elements tend to
become negative ions if possible, or at least theytend to attract electrons.
They are electron-acceptors
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G.
Selvaduray,
SJS
U,
Fall2006
Electronegativity
Tendency of an atom to gain an electron
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G.
Selvaduray,
SJS
U,
Fall2006
Table of Electronegativities
Source: L. Pauling, Nature of the Chemical Bond
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G.
Selvaduray,
SJSU,
Fall2006
Electronegativity & Atomic
Bonding
Fraction Covalent Bonding =
Fraction Ionic Bonding =
)25.0exp(
2E
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