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Atoms tiny wonders worth studying Energy states of electrons in atoms are represented by this formula. Understand all the symbols and implications of this formula. . The Hydrogen Spectrum. Balmer’s finding Balmer series, n i = 2; snd n f = 3, 4, 5, ... Rydberg’s formula Rydberg constant.

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tiny wonders worth studying

Energy states of electrons in atoms are represented by this formula. Understand all the symbols and implications of this formula.


the hydrogen spectrum
The Hydrogen Spectrum

Balmer’s findingBalmer series, ni = 2; snd nf = 3, 4, 5, ...

Rydberg’s formula

Rydberg constant

Wave number = – R (–– – ––)

1 1nf2ni2


the discovery of x rays
The Discovery of X-rays

Rontgen’s letter publish in Nature (Jan 23, 1896) with a photo showing a hand skeleton of his wife proclaimed the discovery of X-rays. (

Image of rabbit

X-ray image of Mrs. Rontgen’s hand


Tell the story of X-ray discovery.

generation of x rays
Generation of X-rays

What is the principle of X-ray generation?


characteristic x rays and energy levels of electrons in elements
Characteristic X-rays and energy levels of electrons in elements

What are characteristic X-rays and why they are generated?


moseley s law
Moseley’s Law

= h  = E

What is Moseley’s law and how it impacts science?


x ray diffraction explained
X-ray Diffraction Explained

Typical diffraction diagram of a quasicrystal, exhibiting 5-fold or 10-fold rotational symmetry


crystal structures revealed by x ray diffractions
Crystal Structures Revealed by X-ray Diffractions

X-ray diffraction revealed structures of many substances and impacted science and engineering development. Two are shown.



Discovery of Radioactivity

Methodology in Becquerel’s discovery of radioactivity is intriguing and interesting.

How do you explain the discovered phenomenon?

What & why?



Properties of Radioactive Rays

What is radioactivity?



Rutherford -particle Scattering Experiment

What is the alpha scattering experiment?

What did he observed, and how he explained it?



The Rutherford Atoms

Rutherford’s Conclusion

Radius of atoms: 1e-10 m

H 37 He 50 Li 150 F 71 Fr 170

Radius of nuclei: 1e-15 m

rnuc= 1.2 A1/3 fm(1E-15)



The Bohr Atoma tiny solar system

Bohr applied the Idea of Max Planck, and used results from Rutherford. He made an assumprion:

m v r = h/2His results are given next

What is the Bohr atom?How did he arrive such a model? If U care



Energy States of Electrons in the Bohr Atom

Results of Bohr atom

m v r = h/2

En =



A Quantum Mechanical View of Energy States

In a large system, the energy states form a band. As the system gets smaller, energy states progressively became discrete.

Quantum mechanics is required to deal with microscopic systems and discrete energy states.



The Development of Quantum Mechanics

Max Planck’s photon: E = h nRutherford atomThe Bohr atom (solar system) Heisenberg’s uncertainty principleLouis de Broglie (mater wave): = h / m vSchrodinger: Treat particles as waves

What are the philosophies behind quantum?



Quantum Mechanical View of Energy States of Electrons in the Atoms

Diagram energy states in atoms and explain the periodic table.

Atomic Orbitals

4f– – – – – – –

4d– – – – –

4p– – –

4s– 3d– – – – –

3p– – –


2s– 2p– – –




Quantum Mechanics Led to and the Periodic Table of Elements

Filling electrons in energy states gives the electronic configurations of all elements.

Electronic configurations of some light elements

Ne 1s2 2s22p6

F 1s2 2s22p5

O 1s2 2s22p4

N 1s2 2s22p3

C 1s2 2s22p2

B 1s2 2s22p1

Be 1s2 2s2

Li 1s2 2s1

He 1s2

H 1s1

Atomic Orbitals

4f– – – – – – –

4d– – – – –

4p– – –

4s– 3d– – – – –

3p– – –


2s– 2p– – –



the time line of our understanding of the atomic nuclei
The time line of our understanding of the atomic nuclei

Yin Yang and Primal Substance

1704 I. Newton – Solid body

1803 J. Dalton – atomic theory

1832 M. Faraday – electrolysis

1879 W. Crookes – discovered electrons

1886 W. Rontgen – X-rays H. Becquerel – radioactivity Goldstein – kanal rays

1897 J.J. Thomson – e/m ratio - Canal rays (H atom)

1898 E. Rutherford – studied radioactivity

1900 Soddy – transmutation of elements

1911 E. Rutherford – dense +ve nuclei

1914 H.G.J. Moseley – Moseley law

1922 N. Bohr – Bohr atom model

1923 de Broglie – particles as waves

1927 Heisenberg – uncertainty principle

1927 Cockcroft /Walton – split the atom

Some facts about atoms:

Radii of atoms ~ 1e-10 m (Å) most space occupied by electrons

Radii of atomic nuclei ~ 1e-15 m (fm) most mass concentrated in nuclei


properties of protons
Properties of Protons

1886 Goldstein discovered canal rays

1898 Wien and Thomson identified them as nuclei of H and determined some properties of protons

The atomic number used in Moseley’s law turns out to be the number of protons in the nuclei

Protons were thought to be fundamental particles

Rest1.6726231x10–27 kg mass1.00727647 amu 938.2723 MeV


Magnetic 2.7928474 Nmoment

Electric+1 atomic chargecharge

What is a proton?


discovery of neutrons
Discovery of Neutrons

It has been shown by Bothe and others that beryllium when bombarded by -particles of polonium emits a radiation of great penetrating power, .…

Be +  = C + n + Energy B + n = Li + 

It is to be expected that many of the effects of a neutron in passing through matter should resemble those of a quantum of high-energy, and it is not easy to reach the final decision between the two hypotheses.

Up to the present, all the evidence is in favour of the neutron, while the quantum hypothesis can only be upheld if the conservation of energy and momentum be relinquished at some point.

James Chadwick, Feb. 23, 1932

How was neutron discovered, and what is it?


neutron scattering techniques
Neutron Scattering Techniques


12 October 1994

The Royal Swedish Academy of Sciences has decided to award the 1994 Nobel Prize in Physics for pioneering contributions to the development of neutron scattering techniques for studies of condensed matter with one half to Professor Bertram N. Brockhouse, McMaster University, Hamilton, Ontario, Canada, for the development of neutron spectroscopy

and one half to Professor Clifford G. Shull, MIT, Cambridge, Massachusetts


applications of neutrons from a research reactor for studying structures and dynamics
Applications of neutrons from a research reactor for studying structures and dynamics



Discovery of neutron in atomic nuclei led to the concept of isotopes.

Atomic weight

Na 23Mg 24.3Cl 35.5Ar 40.K 39Ca 40Cu 63.5

Why atomic weights are not all integers?

Can atoms of an element have different number of neutrons?

What are isotopes?

What are isotopes?

What are stable isotopes of C, Cl, Ca?


deuterium and isotopes of hydrogen
Deuterium and Isotopes of Hydrogen

Does hydrogen have isotopes?

How to separate isotopes?

How are their properties different?

H2 HD D2

Triple point /K 13.96 16.60 18.73

Vapor pressure 128.6 92.8 54.0 at TP

Heat of vapori- 117 159 197 zation at TP

Boiling point (K) 20.39 22.13 23.67

Heat of vapori- 903 1074 1225zation at BP

Harold C. Urey (1893-1981)1934 Nobel Laureate in Chemistry for his discovery of heavy hydrogen.


urey experiment about life
Urey Experiment About Life

The early Earth atmosphere of NH3, CH4, H2O, under discharge produced organic matter including aminoacids that are essential compounds for life form.


atomic mass abundance and atomic weight
Atomic Mass, Abundance and Atomic Weight

Isotope atomicmass Abundance atomicmass*abundance

1H 1.00782503 0.99985 1.007674

2H 2.014102 0.000148 0.000298

3H 3.016049 Trace

---- +________

Atomic weight for H = 1.007674 + 0.00298 = 1.007972

Practice the evaluation of atomic weight of an element using the same method as this example shows.


notations for nuclides
Notations for Nuclides

Representations of a nuclide




How isotope differ from nuclide?

How are nuclides represented?

3T13He212C616O8235U92 238U92 234U92



the quarks
The Quarks

Based on the properties and relationships of particles known in 1962, Gell-Mann in the US and Y. Neémen of Israel predicted the existence and properties of some unknown particles in considerable detail. Gell-Mann and Zweig from Caltech suggested that some heavy particles such as protons and neutrons (called baryons) were made up from three entities called quarks, so named by Murray Gell-Mann after a quote "three quarks for muster Mark, sure he hasn't got much of a bark, etc..." from the novel Finnegan's Mark. J. Joyce, author of the novel, used quarks to rhyme with Mark, bark, lark etc....


the standard model
The Standard Model

A Simplified Universe

Generation First Second Third

Quarksu, d c, s t, b

Leptonse, nem,nm t, nt

Scientific progress often involves establishing conventional wisdom. Other times, it is more a matter of defying it.



X-ray and Neutrons in the News

  • X-Ray Optical Systems, Inc., used the ATP funding to develop processes to fabricate and predict the performance of new “capillary optics” technology, which can bend and focus both X-rays and neutrons. Follow-on efforts to develop medical, industrial, and scientific applications are beginning to pay off for both the company and the nation. For example:
  • An instrument that generates beams with 100 times the intensity of other compact X-ray sources is an early spin-off of the project.
  • The new optics can identify and analyze the structure of proteins four to 10 times faster than conventional methods, a benefit in drug design.
  • Among industrial applications, the new optics offer a four- to 16-fold increase in X-ray intensity that is accelerating the development and monitoring of magnetic data-storage materials.
  • And this is only the beginning.“We have more active collaborations than we have employees, and we have identified more application areas than we have employees ... it’s an exciting time,” says David Gibson, the company president.