Atomic Structure Report

NATIONAL UNIVERSITY OF JAEN
PROFESSIONAL SCHOOL OF ENGINEERING

MECHANICAL AND ELECTRICAL
ISSUE
ATOMIC STRUCTURE
TEACHER
ING. JOSE A. VASQUEZ WALLS
COURSE
MATERIAL SCIENCE
MEMBERS
LUIS M. VASQUEZ VASQUEZ
CUBAS QUEVEDO SALOMON
Jaén, April 14, 2016

INTRODUCTION
Solid solution hardening:
In some alloys the solvus lines of the coherent precipitates

are located between the room temperature and the aging
temperature.
Strain hardening:
It can be applied to all aluminum alloys that have the

plasticity necessary for forming processes. This requirement
occurs in those alloys with compositions lower than the
maximum solubility of the alloy at the eutectic temperature;
however, cold deformation (lamination) occurs in those alloys
that do not harden by precipitation.
Reinforcement hardening:
One way to achieve alloys that are stable at high

temperatures consists of reinforcement with particles
insoluble in aluminum that are stable at these temperatures,
called dispersoids.
GOALS
 Learn history and concept of the atom.

 See the importance of atomic structure in the
resistance of materials.
 Classify the different existing atomic models.
 Learn the evolution during history about the atom.
 Understand what the mass number and atomic

number of an element are for.
 Learn the elements that make up an atom.
THE ATOM
The name "atom" comes from the Latin atomum , 'uncut,

portionless, indivisible'. The concept of the atom as a basic and
indivisible block that makes up the matter of the universe was
postulated by the atomistic school in Ancient Greece . However,
they were not seriously considered by scientists until the 19th
century , when they were introduced to explain certain chemical
laws. With the development of nuclear physics in the 20th century
, it was proven that the atom can be subdivided into smaller
particles .
Atoms are very small objects with equally tiny masses: their
diameter and mass are on the order of a billionth of a meter and a
quadrillionth of a gram . They can only be observed using special
instruments such as a scanning tunneling microscope . More than
99.94% of the mass of the atom is concentrated in its nucleus,
generally distributed approximately equally between protons and
neutrons.
SUBATOMIC PARTICLES
 Proton : Found in the nucleus. Its mass is 1.6×10 -27 kg. It has
a positive charge equal in magnitude to the charge of the
electron. The atomic number of an element indicates the
number of protons it has in the nucleus.
 Electron : Found in the cortex. Its mass is approximately
9.1×10 -31 kg . It has a negative electrical charge (-1.602×10 -
19
C ).
 Neutron : Found in the nucleus. Its mass is almost the same
as that of the proton. It does not have an electrical charge.
Electrons, particularly the external mass, determine most of the

mechanical, electrical, chemical, etc. properties of atoms, and
thus a basic knowledge of atomic structure is important in the
basic study of engineering materials.
Atomic number and mass number
The identity of an atom and its properties are given by the

number of particles it contains. What distinguishes some
chemical elements from others is the number of protons that their
atoms have in the nucleus. This number is called the Atomic
Number and is represented by the letter Z. It is placed as a
subscript to the left of the corresponding element symbol.
The Mass number tells us the total number of particles in the

nucleus, that is, the sum of protons and neutrons. It is
represented by the letter A and is placed as a superscript to the
left of the element symbol. It represents the mass of the atom
measured in amu, since that of the electrons is so small that it
can be neglected.
In the example, we would have an atom of the element

neon, with 10 protons in its nucleus and 10 electrons in its
shell (it is neutral). It would also have: 22-10 = 12
neutrons.
ATOMIC MODELS
An atomic model is a structural representation of an atom,

which attempts to explain its behavior and properties. Over
time there have been several atomic models and some more
elaborate than others:
Dalton model
It was the first atomic model with
scientific bases, it was formulated in 1803
by John Dalton , who imagined atoms as
tiny spheres. This first atomic model
postulated:
 Matter is made up of very small particles called atoms, which
are indivisible and cannot be destroyed.
 The atoms of the same element are equal to each other, they
have their own weight and their own qualities. The atoms of
the different elements have different weights.
 Atoms remain undivided, even when combined in chemical
reactions.
 Atoms, when combined to form compounds, have simple
relationships.
 Atoms of different elements can combine in different
proportions and form more than one compound.
 Chemical compounds are formed by joining atoms of two or
more different elements.
However, it disappeared before Thomson's model since it does
not explain cathode rays, radioactivity or the presence of
electrons (e-) or protons (p+).
Thomson model
After the discovery of the electron
in 1897 by Joseph John Thomson ,
it was determined that matter was
composed of two parts, a negative
and a positive. The negative part
was made up of electrons, which
were, according to this model,
immersed in a mass of positive
charge like raisins in a cake or
grapes in jelly. Later Jean Perrin
proposed a modified model based
on Thomson's where the "raisins"
(electrons) were located on the outside of the "cake" (protons).
To explain the formation of ions, positive and negative, and the
presence of electrons within the atomic structure, Thomson
devised an atom resembling a fruit pie. A positive cloud that
contained the small negative particles (electrons) suspended in it.
The number of negative charges was adequate to neutralize the
positive charge. In the event that the atom lost an electron, the
structure would remain positive; and if he won, the final charge
would be negative. In this way, he explained the formation of
ions; but it left the existence of the other radiations unexplained.
Rutherford model
This model was developed by physicist
Ernest Rutherford based on the results
obtained in what is now known as the
Rutherford experiment in 1911. It
represents an advance over Thomson's
model, since it maintains that the atom is
composed of a positive and a negative
part. However, unlike the previous one, it postulates that the
positive part is concentrated in a nucleus, which also contains
virtually all the mass of the atom, while the electrons are located
in a crust orbiting the nucleus in circular or elliptical orbits with a
space void between them. Despite being an obsolete model, it is
the most common perception of the atom by the non-scientific
public.
Rutherford predicted the existence of the neutron in 1920 , for
that reason in the previous model (Thomson), it is not mentioned.
Bohr model
This model is strictly a model of the
hydrogen atom taking Rutherford's
model as a starting point. Niels
Bohr tries to incorporate the
phenomena of absorption and
emission of gases, as well as the
new theory of energy quantization
developed by Max Planck and the phenomenon of the
photoelectric effect observed by Albert Einstein .
"The atom is a small solar system with a nucleus in the center
and electrons moving around the nucleus in well-defined orbits."
Orbits are quantized (e-s can only be in certain orbits)
 Each orbit has an associated energy. The outermost is the

most energy.
 Electrons do not radiate energy (light) as long as they remain
in stable orbits.
 Electrons can jump from one orbit to another. If it moves from
one of lower energy to one of higher energy, it absorbs a
quantum of energy (a quantity) equal to the difference in
energy associated with each orbit. If it goes from a higher one
to a lower one, it loses energy in the form of radiation (light).
Bohr's greatest success was to explain the emission spectrum of
hydrogen, but only the light of this element provides a basis for
the quantum character of light, the photon is emitted when an
electron falls from one orbit to another, being a pulse of radiated
energy.
Bohr could not explain the existence of stable orbits and for the
quantization condition.
Bohr found the angular momentum of the electron to be h/2π by
a method he cannot justify.
Sommerfeld model
Bohr 's atomic model
worked very well for the
hydrogen atom , however,
in the spectra made for
atoms of other elements it
was observed that electrons
of the same energy level
had different energies,
showing that there was an error in the model. His conclusion was
that within the same energy level there were sublevels, that is,
slightly different energies. Furthermore, from a theoretical point of
view, Sommerfeld had found that in certain atoms the speeds of
the electrons reached an appreciable fraction of the speed of light
. Sommerfeld studied the question for relativistic electrons.
The German physicist Arnold Sommerfeld , with the help of Albert
Einstein 's Theory of Relativity , made the following modifications
to Bohr's model:
1. Electrons move around the nucleus, in circular or elliptical

orbits.
2. Starting from the second energy level, there are two or
more sublevels at the same level.
3. The electron is a tiny electric current.
Consequently, Sommerfeld's atomic model is a generalization of
Bohr's atomic model from a relativistic point of view, although he
could not demonstrate the forms of emission of elliptical orbits, he
only ruled out their circular shape.
SCHRÖDINGER MODEL
Location probability density of an

electron for the first energy levels.
After Louis-Victor de Broglie proposed

the wave nature of matter in 1924 ,
which was generalized by Erwin
Schrödinger in 1926 , the model of the
atom was updated again.
In Schrödinger's model, the conception of electrons as tiny
charged spheres that revolve around the nucleus is abandoned,
which is an extrapolation of experience at a macroscopic level to
the tiny dimensions of the atom. Instead, Schrödinger describes
electrons by means of a wave function , the square of which
represents the probability of their presence in a bounded region
of space. This probability zone is known as an orbital .
Dirac model
The Dirac model uses very similar assumptions to the
Schrödinger model although its starting point is a relativistic
equation for the wave function, the Dirac equation . The Dirac
model allows us to incorporate the electron spin in a more natural
way. It predicts energy levels similar to the Schrödinger model by
providing appropriate relativistic corrections.
Later models
Following the establishment of the Dirac equation, quantum
theory evolved into quantum field theory . The models that
emerged in the 1960s and 1970s allowed us to build theories of
nucleon interactions. The old atomic theory was confined to the
explanation of the electronic structure that continues to be
adequately explained by the Dirac model complemented with
corrections arising from quantum electrodynamics . Due to the
complication of strong interactions, only approximate models of
the structure of the atomic nucleus exist. Among the models that
try to account for the structure of the atomic nucleus are the liquid
drop model and the shell model .
Subsequently, starting in the 1960s and 1970s, experimental
evidence and theoretical models appeared suggesting that the
nucleons (neutrons, protons) and mesons ( pions ) that constitute
the atomic nucleus would be made up of more elementary
fermionic constituents called quarks . The strong interaction
between quarks entails complicated mathematical problems,
some of which have not yet been exactly solved. In any case,
what is known today makes it clear that the structure of the
atomic nucleus and the particles that form the nucleus are much
more complicated than the electronic structure of atoms. Since
chemical properties depend exclusively on the properties of the
electronic structure, it is considered that current theories
satisfactorily explain the chemical properties of matter, the study
of which was the origin of the study of atomic structure.
CONCLUSIONS
 We learned history and concept of the atom.
 We saw the importance of atomic structure in the

resistance of materials.
 We classify the different existing atomic models.
 We learned evolution during the story about the atom.
 We understood what the mass number and atomic

number of an element are for.
 We learned the elements that make up an atom.
BIBLIOGRAPHY
 https://www.google.com.pe/?
gfe_rd=cr&ei=7AoUV_fwAY-w8weX5YKoBA
 http://www.eis.uva.es/~qgintro/atom/atom.html
 Encarta
 http://prepaunivas.edu.mx/v1/images/pdf/
libros/quimica_I.pdf
 http://www.hezkuntza.ejgv.euskadi.eus/r43-
20621/es/contenidos/informacion/zisapro/
es_5807/adjuntos/quimica-n3.pdf

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NATIONAL UNIVERSITY OF JAEN

PROFESSIONAL SCHOOL OF ENGINEERING

Jaén, April 14, 2016

Solid solution hardening:

In some alloys the solvus lines of the coherent precipitates

It can be applied to all aluminum alloys that have the

One way to achieve alloys that are stable at high

 Learn history and concept of the atom.

 Classify the different existing atomic models.

 Learn the evolution during history about the atom.

 Understand what the mass number and atomic

 Learn the elements that make up an atom.

The name "atom" comes from the Latin atomum , 'uncut,

Electrons, particularly the external mass, determine most of the

The identity of an atom and its properties are given by the

The Mass number tells us the total number of particles in the

In the example, we would have an atom of the element

An atomic model is a structural representation of an atom,

 Each orbit has an associated energy. The outermost is the

1. Electrons move around the nucleus, in circular or elliptical

Location probability density of an

After Louis-Victor de Broglie proposed

 We learned history and concept of the atom.

 We saw the importance of atomic structure in the

 We classify the different existing atomic models.

 We learned evolution during the story about the atom.

 We understood what the mass number and atomic

 We learned the elements that make up an atom.

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