S.MORRIS 2006
Banphuepittayasan School Udonthani
HELIUM ATOM
+N
N
+-
-
proton
electron neutron
Shell
What do these particles consist of?
Particle
proton
neutron
electron
Charge
+ charge
-charge
No charge
1
1
0
Mass
ATOMIC STRUCTUREATOMIC STRUCTURE
the number of protons in an atom
the number of protons and neutrons in an atom
HeHe22
44 Atomic mass
Atomic number
number of electrons = number of protons
Notation
3545358035Br
1822184018Ar
2020204020Ca
e–n0p+MassAtomic
11 p+12 n°
2e– 8e– 1e–
Na
8 p+8 n°
2e– 6e–
O
4 p+5 n°
Be
5 p+6 n°
B
13 p+14 n°
Al
3 p+
3 n02e– 1e–
6Li 7Li
3 p+
4 n02e– 1e–
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Types of RadiationTypes of Radiation
e01−
He42
γ00
• Alpha (Alpha (άά) – a positively ) – a positively charged helium isotopecharged helium isotope
we usually ignore the charge because it we usually ignore the charge because it involves electrons, not protons and neutronsinvolves electrons, not protons and neutrons
•Beta (Beta (ββ) – an electron) – an electron
•Gamma (Gamma (γγ) – pure energy; ) – pure energy; called a ray rather than a particlecalled a ray rather than a particle
Other Nuclear ParticlesOther Nuclear Particles
e01+
n10
H11
• NeutronNeutron
• Positron – a positive electronPositron – a positive electron
•Proton – usually referred to as Proton – usually referred to as hydrogen-1hydrogen-1
Nuclear Particle (อนุภาคทางนิวเคลียร์)
Penetrating Ability Penetrating Ability ((การทะล ุผ ่านการทะล ุผ ่านส ิ่งก ีดขวางส ิ่งก ีดขวาง ))
Nuclear ReactionsNuclear Reactions• Alpha emissionAlpha emission
Note that mass number (A) goes down by 4 and atomic number (Z) goes down by 2.
Nucleons (nuclear particles… protons and neutrons) are rearranged but conserved
Nuclear ReactionsNuclear Reactions• Beta emissionBeta emission
Note that mass number (A) is unchanged and atomic number (Z) goes up by 1.
Other Types of Nuclear ReactionsOther Types of Nuclear ReactionsPositron (Positron (00
+1+1ββ ): a positive electron): a positive electron
Electron capture: Electron capture: the capture of an electron
207 207
Learning Check
What radioactive isotope is produced in the following bombardment of boron?
10B + 4He ? + 1n
5 2 0
Artificial Nuclear ReactionsArtificial Nuclear Reactions
Example of a Example of a γγ reaction reaction is production of is production of
radioactive radioactive 3131P for use in studies of P P for use in studies of P
uptake in the body.uptake in the body.
31311515P + P + 11
00n ---> n ---> 32321515P + P + γγ
Transuranium ElementsTransuranium Elements
Elements beyond 92 Elements beyond 92 (transuranium)(transuranium) made made
starting with an starting with an γγ reaction reaction
2382389292U + U + 11
00n ---> n ---> 2392399292U + U + γγ
2392399292U U ---> ---> 239239
9393Np + Np + 00-1-1ββ
2392399393Np Np ---> ---> 239239
9494Pu + Pu + 00-1-1ββ
Examples of Radioactive DecayAlpha Decay
Po Pb + He
Beta Decay p n + en p + e
C N + eGamma Decay
Ni Ni + γ(excited nucleus)
Nuclear FissionNuclear Fission
Nuclear FissionNuclear FissionFission is the splitting of atomsFission is the splitting of atoms
These are usually very large, so that they are not as stableThese are usually very large, so that they are not as stable
Fission chain has three general steps:Fission chain has three general steps:
1.1. Initiation.Initiation. Reaction of a single atom starts the chain Reaction of a single atom starts the chain
(e.g., (e.g., 235235U + neutron)U + neutron)
2.2. PropagationPropagation. . 236236U fission releases neutrons that U fission releases neutrons that
initiate other fissionsinitiate other fissions
3. 3. ___________ ___________ . .
Stability Stability of Nucleiof Nuclei
• Out of > 300 stable isotopes:
EvenEven OddOdd
OddOdd
EvenEven
ZZNN
157157 5252
5050 55
31311515PP
191999FF
2211H, H, 66
33Li, Li, 101055B, B, 1414
77N, N, 1801807373TaTa
Representation of a fission process.
Nuclear Fusion
Fusion small nuclei combine
2H + 3H 4He + 1n +
1 1 2 0
Occurs in the sun and other stars
Energy
Fusion Reactions
Isotopes
• Atoms that have the same number of protons but different numbers of neutrons are called isotopes.
Isotopes of Hydrogen
1 p+ 1 e- 1 p+
1 n 1 e- 1 p+2 n 1 e-
Protium Deuterium Tritium
(ordinary hydrogen) (heavy hydrogen) (radioactive hydrogen)
H1
1H2
1H3
1
Ralph A. Burns, Fundamentals of Chemistry 1999, page 100
H-2 H-3H-1
Isotopes of Magnesium
Atomic symbol Mg Mg Mg
Number of protons 12 12 12
Number of electrons 12 12 12
Mass number 24 25 26
Number of neutronsneutrons 12 13 14
2412
2512
2612
Isotope Notation Mg-24 Mg-25 Mg-26
Timberlake, Chemistry 7th Edition, page 64
12p+
12n0
12p+
13n0
12p+
14n0
12e- 12e- 12e-
Isotopes of Three Common Elements
Element SymbolFractional
AbundanceAverage Atomic Mass
Carbon
Chlorine
SiliconSiSiSi
282930
27.97728.97629.974
92.21% 4.70% 3.09%
12 6
13 6
3517
3717
2814
2914
3014
12.01
35.45
28.09
1.11%13.00313C
99.89%12 (exactly)12C
Mass (amu)
75.53%
24.47%36.96637Cl
34.96935Cl
Mass
Number
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