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