Length scale of the nature
10−14
10−12
m
10−8
10−10
10−6
10−4
10−2
size of the nucleus
wavelength of X-ray
radius of the atoms
size of proteins
The microscopic world
atomic nucleus, radioactive decays
size of the cells
thickness of a pinhair
trees, people, flowers
Irén Bárdos-Nagy
10−6
10−4
10−2
1
nm
102
104
106
108
Sructure of atom
Building elements of atomic structure:
the electron cloud
name/where
charge
mass (kg)
(elementary)
atomic mass unit
(chemical properties)
Structure of nucleus
electron/outside
the nucleus
-1
9,1*10-31
proton/inside
the nucleus
+1
1,66*10-27
1,007277
neutron/inside
the nucleus
0
1,67*10-27
1.008665
0,0005486
the nucleus
(radioactivity)
proton
neutron
the charge of the electron:
1,6*10-19
C
The figurative depiction of the He-4 atom
Proton and/or neutron = nucleon
The atomic and the mass number
Stability of the nucleus
Coulomb force:
electrostatic repulsion between the positively charged protons
Nuclear force:
very strong attractive force
act only on short - range (10-14 m)
do not depend on the charge
E (MeV)
The nucleons have definite energy levels (MeV scale)
Quantized energy for the nucleus
Binding energy:
Total mass of 2 protons:
Total mass of 2 neutrons:
Total mass of nucleons:
2.01456 amu
2.01732 amu
4.03188 amu
Mass of the He atom:
4. 00153 amu
Mass defect (Δm):
0.03035 amu
4
Z atomic number
A mass number
Binding energy of
4
2He:
( ΔE=Δm*c2)
Nuclear binding energies of the different elements
28.3 MeV
2He
nucleus
Isotopes:
Table of isotopes
number of neutrons is different
proton number
number of protons is the same
mass number
atomic weight
The chemical properties are the same!!
Table of isotopes
neutron number
Radioactive decays and particles
decay
proton number
α
α
particle =
4
2
He nucleus
β−
β − particle = electron
β+
β + particle = positron
K – electron capture
Isomeric transition
neutron number
particles
characteristic X – ray photon
γ – radiation (photon)
The β
The α decay
−
decay
A
Z
X → Z +A1Y + β − + ν
electron
X → ZA−−42Y + 24α
leave the nucleus
antineutrino
Examples:
The energy of the emitted
α particle is constant in the
case of a given nuclid:
line spectrum (MeV)
14
6
C →147N + β − + ν
40
19
K → 2040Ca + β − +ν
59
26
Fe→ 2759Co + β − +ν
131
53
Nβ particles
A
Z
−
I →131
54 Xe + β + ν
Kinetic energy
continuous spectrum
The β + decay
A
Z
K – electron capture (inverse β- decay)
characteristic X-ray emission
X → Z −A1Y + β + + ν
1
1
p + β − →01n +ν
positron
leave the nucleus
neutrino
Examples:
40
19
C →115B + β + + ν
11
6
13
7
N →136C + β + + ν
52
26
18
9
52
Fe→ 25
Mn + β + + ν
F →188 0 + β + +ν
Examples:
continuous spectrum
40
K + β − →18
Ar + ν
Cr + β − →51
23V + ν
51
24
123
53
I + β − →123
52Te + ν
The γ decay
Summary
Prompt γ decay
There is no change of the number of protons and neutrons
Isomeric transition
99
42
β−
γ
66 hours
6 hours
Mo→9943m Tc →99
43Tc
opportunuty for separation
Pair production
annihilation
positron
electron
electron
positron
E ph ⇒ me − c 2 + me + c 2
~ 1MeV
me − c 2 + me + c 2 ⇒ 2 ⋅ E ph
~ 0.5 MeV