Atomicstructure

ATOMIC STRUCTURE
ATOMIC STRUCTURE
Subject Physics and Chemistry
Course/Level 3º ESO/4º ESO
Primary Learning Objective Students will be able to define atom and element in their own words, and demonstrate an understanding of the structure of atoms by creating a
physical model. On the other hand, students will understand that the periodic table is a graphic representation of all known elements and that it
contains information about the properties of each element.
Subject Content 1. Evolution of the atomic model.
1.1. Some early ideas on matter.
1.2. Dalton’s atomic model.
1.3. Crooke’s tube.
1.4. The electron discovery experiment.
1.5. The charge of the electron.
1.6. Gold foil experiment.
1.7. Bohr’s atomic model.
1.8. Discovery of the neutron.
1.9. Charge-cloud model.
1.10. The Standard model.
2. Particles in the atom.
2.1. Particles.
2.2. Isotopes.
3. Periodic table.
3.1. History of the periodic table.
3.2. Electron configuration.
3.3. Periodic patterns.
3.4. Elements in the human body: top ten.
3.5. Trends in the periodic table.
Language Content /
Communication
Vocabulary Continuous , metals, non-metals, metalloids, alkali metals, alkaline earth metals, transition elements, halogens, noble
gases, lanthanides, actinides, inner transition elements, hydrogen, properties, atomic structure, particles, isotopes, average
atomic mass, atomic number, mass number, electron configuration, group, period, model, etc.
Structures Routines: How do we know atoms exist? Where does matter come from? How are elements formed? Are all atoms of an
element the same? How do we measure atoms if they are so small?
Contents: Conditionals, present, future, comparatives.
Classroom management: Take out your notebook/recorder/pen, write down the following sentence, right! / you're right,
well done! / very well! / good job , etc.
Discourse type Exposition, description, argument.
Language skills Writing, reading, speaking and listening
Activities The presentation includes different activities with an explanation in order to the students answer a question or solve a problem.
LESSON PLAN
Pepi Jaramillo Romero
Dpto. Física y Química
IES Rodríguez Moñino

ATOMIC STRUCTURE
METHODOLOGY
Organization and class distribution / timing The number of sessions considered to develop the contents on this unit are at least 8 sessions of 50 minutes each one (+ 2 week final Project)
It’s very important to point out that the methodology will be active and participatory in order to facilitate both individual and group learning. For that, teacher
observation is very important during student's work.
Key Competences Language proficiency Know, acquire and apply the vocabulary of the subject.
Exercising a comprehensive reading of texts related to the topic.
Mathematical Competence Be able to mathematically calculate protons, neutrons and electrons from atomic mass and number mass.
Calculate the average atomic mass of an atom from isotopic data.
Digital competence and treatment of
information
I use PDI to explain content and implementation of web quest by students.
Make the online activities.
Social and civic competences Fostering respect between and other values like cooperation, coeducation when they work in groups.
Autonomy and personal initiative To be autonomous for individual activities.
Evaluation Acquired content knowledge (*) Describe the development of the concept of the atom from Democritus to the modern day.
Compare and contrast the continuous and discontinuous theories of matter.
Summarize the five essential points of Dalton’s atomic theory.
List the properties of protons, neutrons, and electrons.
Describe the history of the periodic table and the contributions of Meyer, Newlands, Mendeleev, etc.
Describe the relationship between atomic number and atomic mass.
Describe our modern periodic table and how the elements are arranged.
Distinguish between core and valence electrons.
Identify each block of the periodic table and be able to determine which block each element belongs based on its
electron configuration.
Describe the relationship between outer electron configuration and group number.
Locate the following groups of elements on the periodic table: alkali metals, alkaline earth metals, halogens,
noble gases, transition elements, lanthanides, and actinides.
Instruments The unit will be evaluated daily with:
Individual participation in classroom activities and homework.
Works in groups.
Notebook.
Behaviour.
Tests.
Glossary.
Conceptual maps
Final Project.
(*) Depends on the student’s level.

1. Evolution of the atomic model.
1.1. Some early ideas on matter.
1.2. Dalton’s atomic model.
1.3. Crooke’s tube.
1.4. The electron discovery experiment.
1.5. The charge of the electron.
1.6. Gold foil experiment.
1.7. Bohr’s atomic model.
1.8. Discovery of the neutron.
1.9. Charge-cloud model.
1.10. The Standard model.
2. Particles in the atom.
2.1. Particles.
2.2. Isotopes.
3. Periodic table.
3.1. History of the periodic table.
3.2. Electron configuration.
3.3. Periodic patterns.
3.4. Elements in the human body: top ten.
3.5. Trends in the periodic table.
OUTLINE
ATOMIC STRUCTURE

ATOMIC STRUCTURE
1. EVOLUTION OF THE ATOMIC MODEL
 How do we know atoms exist?
 How do we know that electrons,
protons, and neutrons exist?
 Where does matter come from?
 How are elements formed?
 Are all atoms of an element the same?
 How do we measure atoms if they are
so small?

ATOMIC STRUCTURE
1.1. SOME EARLY IDEAS ON MATTER
Democritus (Thracian, born 470 B.C.)
Actually proposed the word atom (indivisible)
because he believed that all matter consisted
of such tiny units with voids between, an idea
quite similar to our own beliefs. He expanded
upon the work of Leucippus, a mentor of his,
who believed matter was actually finite and
not limitless. Democritus proposed that all
matter is composed of fundamental, indivisible
particles that he called atoms. The essential
ideas behind his theory are the following:
1.Everything is composed of “atoms,” which are
physically indivisible.
2.Atoms are indestructible and constantly in
motion.
3.There is empty space between atoms.
Empedocles (Greek, born in Sicily, 490 B.C.)
Suggested there were only four basic seeds:
earth, air, fire, and water. The elementary
substances (atoms to us) combined in
various ways to make everything.
Aristotle (Greek, born 384 B.C.)
Added the idea of “qualities” – heat, cold,
dryness, moisture – as basic elements which
combined as shown in the diagram
Aristotle, who was considered a greater “authority,” taught against it and influenced other
philosophers to reject the ideas of Democritus. It would be thousands of years before his ideas were
reviewed and found to be consistent with more recently available scientific evidence.
However, this idea was not well-received at the time.

ATOMIC STRUCTURE
1.2. DALTON’S ATOMIC MODEL
From his experiments and observations, as well as the
work of contemporary scientists, Dalton proposed a new
theory of the atom around 1803. The general tenets of this
theory were as follows:
1. All matter is composed of extremely small particles. Dalton, like
Democritus, called these particles “atoms”.
2. Atoms of a given element are identical in size, mass, and other
properties. Atoms of different elements differ in size, mass, and
other properties.
3. Atoms cannot be subdivided, created, or destroyed.
4. Atoms of different elements can combine in simple whole
number ratios to form chemical compounds.
5. In chemical reactions, atoms are combined, separated, or
rearranged.

ATOMIC STRUCTURE
1.3. CROOKE’S TUBE
In 1877, Sir William Crookes (1832 - 1919) was the British scientist who invented
the cathode ray tube. He was studying how electrical current behaves in a
vacuum tube. His work paved the way to the discovery of the electron.
Video: Crooke's tube
The Crookes tube can be thought of as the forerunner of the modern fluorescent
light tube - a partially evacuated tube fitted with electrodes and filled with
mercury vapor and a little argon gas.

ATOMIC STRUCTURE
1.3. CROOKE’S TUBE

ATOMIC STRUCTURE
1.4. THE ELECTRON DISCOVERY EXPERIMENT
Crookes’s work was later expanded upon by several other scientists. One
scientist in particular, J. J. Thomson, was able to show that cathode rays could be
deflected by a magnetic field.
The particle that J.J.
Thomson discovered in
1897, the electron, is a
constituent of all the
matter we are surrounded
by. All atoms are made of a
nucleus and electrons. He
received the Nobel Prize in
1906 for the discovery of
the electron, the first
elementary particle.
Activity 1.4.1: To know more: Nobel Prize for Physics in 1906

ATOMIC STRUCTURE
Thomson’s Experiment
Crookes’s work was later expanded upon by several other
scientists. One scientist in particular, J. J. Thomson (1897) made
a piece of equipment called a cathode ray tube (it is a vacuum
tube - all the air has been pumped out).
• Using a cathode ray tube, Thomson was able to deflect cathode
rays with an electrical field.

ATOMIC STRUCTURE
Thomson’s Experiment
• The rays bent towards the positive pole,
indicating that they are negatively charged.

ATOMIC STRUCTURE
As shown in the following video:
Activity 1.4.1: Thomson experiment
Activity 1.4.2: Let’s go to the lab! Cathode rays experiment.

ATOMIC STRUCTURE
• He compared the value with the mass/ charge ratio for the lightest
charged particle.
• By comparison, Thomson estimated that the cathode ray particle
weighed 1/1000 as much as hydrogen, the lightest atom.
• He concluded that atoms do contain subatomic particles - atoms are
divisible into smaller particles.
• This conclusion contradicted Dalton’s postulate and was not widely
accepted by fellow physicists and chemists of his day.
• Since any electrode material produces an identical ray, cathode ray
particles are present in all types of matter - a universal negatively
charged subatomic particle later named the electron.
Conclusions

ATOMIC STRUCTURE
J.J. Thomson adopted Lord Kelvin’s model, it became known as the:
Plum Pudding Model.
•The atom was still thought of as a miniscule particle.
•Inside of the atom were the protons and electrons equally distributed.
•The analogy of Plum Pudding was the positive protons were the
pudding and distributed throughout the pudding were the negative
electrons (plums).

ATOMIC STRUCTURE
In 1886, Eugen Goldstein, using equipment similar to
cathode ray tube, discovered particles with charge equal
and opposite to that of electron, but much larger mass. He
named this “canal rays”. Infact these are positively charged
protons, producing a reddish light in the upper part of the
tube. However, Goldstein could not explain this
phenomenon. Rutherford later (1911) found these particles
named protons.
Original form of a Goldstein tube.
This model is a Leybold's Nachfolger product
Probably made second quarter of the 20th century

ATOMIC STRUCTURE
1.5. THE CHARGE OF THE ELECTRON
In 1909, Robert Millikan and Harvey Fletcher devised what is
known as the oil drop experiment to determine the charge
of a single electron.
Using this information, Millikan
calculated the charge of an electron to be
1.5924 × 10−19 coulombs (C). Today, the
accepted value for the charge of an
electron is 1.602176487 × 10−19 C. Despite
the relatively simple apparatus with
which it was determined, Millikan’s value
was within 1% of the currently accepted
value.
Activity 1.5.1: The following video illustrates this experiment and
explains how the charge of an electron was determined: Millikan oil
drop experiment

ATOMIC STRUCTURE
1.6. GOLD FOIL EXPERIMENT
Rutherford began to notice
that alpha particles would
not always behave in
accordance to the plum
pudding model of an atom
when fired at a piece of
gold foil. These
observations stimulated
further research that was
eventually published in
1911 and has been known
ever since as Rutherford's
Gold Foil Experiment.
Activity 1.6.1: To know more: Nobel Prize for Chemistry in 1908

ATOMIC STRUCTURE
Rutherford’s Experiment
He shot high velocity alpha particles (helium nuclei) at an atom then there
would be very little to deflect the alpha particles. He decided to test this with
a thin film of gold atoms.

ATOMIC STRUCTURE
Activity 1.5.1: Here is a short video of his experiment:
Rutherford's experiment
The positive alpha particles were expected to pass through the thin
piece of gold foil.

ATOMIC STRUCTURE
The observations:
(1) Most of the alpha particles pass through the foil un-deflected.
(2) Some alpha particles are deflected slightly as the penetrate the foil.
(3) A few (about 1 in 20,000) are greatly deflected.
(4) A similar small number do not penetrate the foil at all, but are reflected
back toward the source.
Rutherford described it as the most incredible event of his life, "as if
you fired a 15-inch shell at a piece of tissue paper and it came back
and hit you."

ATOMIC STRUCTURE
In 1911, Rutherford cooked up a new model of the atom in which all of the positive
charge is crammed inside a tiny, massive nucleus about ten thousand times smaller than
the atom as a whole. That's equivalent in scale to a marble in the middle of a football
stadium. Rutherford countered by saying that the atom was like a miniature solar system:
the electrons circled the nucleus in wide orbits just as planets orbit the sun. This is the
picture of atoms that most of us still carry around in our heads.

ATOMIC STRUCTURE
 What was to stop the orbiting electrons in
Rutherford's atom quickly (in fact, in about
one hundred-millionth of a second) losing
all their energy and spiraling into the
nucleus?
According to classical
physics, light should be
emitted as the electron
circles the nucleus. A
loss of energy would
cause the electron to be
drawn closer to the
nucleus and eventually
spiral into it.

ATOMIC STRUCTURE
1.7. BOHR’S ATOMIC MODEL
The answer came from a young Dane, Niels Bohr
 In the Bohr Model (1913) the
neutrons and protons occupy a
dense central region called the
nucleus, and the electrons orbit
the nucleus much like planets
orbiting the Sun.
 They are not confined to a planar
orbit like the planets are.

ATOMIC STRUCTURE
1.7. BOHR’S ATOMIC MODEL
• Bohr’s contributions to the understanding of atomic structure:
1. Electrons can occupy only certain regions of space, called orbits.
2. Orbits closer to the nucleus are more stable (they are at lower
energy levels).
3. Electrons can move from one orbit to another by absorbing or
emitting energy, giving rise to a characteristic spectra.
• Bohr’s model could not explain the spectra of atoms heavier than hydrogen.

ATOMIC STRUCTURE
1.8. DISCOVERY OF THE NEUTRON
Activity 1.8.1: To know more:
Nobel Prize for Physics in 1935
In 1932, James Chadwick discovered the
neutron. Chadwick was an English physicist
who was mentored by Rutherford.
His experiment consisted of bombarding beryllium atoms with alpha
particles through a paraffin wax target and studying the effects.
Activity 1.8.2: Neutrons from Berillium

ATOMIC STRUCTURE
1.8. DISCOVERY OF THE NEUTRON
From his analysis, he concluded that the nucleus also contains a particle
which has equal mass to the proton, but unlike the proton, is electrically
neutral - hence the name neutron.
Activity 1.8.3: Here is a short video clip describing Chadwick’s
experiment: Discovery of neutrons
A neutron walks into a restaurant and orders a
couple of drinks. As she is about to leave, she asks
the waiter how much she owes. The waiter replies,
“For you, no charge!!!”
Your funny jokes
always make me
bust up.

In fact, it is impossible to determine the exact location of an
electron. The probable location of an electron is based on how
much energy the electron has.
According to the modern atomic model, at atom has a small
positively charged nucleus surrounded by a large region in which
there are enough electrons to make an atom neutral.
ATOMIC STRUCTURE
1.9. CHARGE-CLOUD MODEL
Modern atomic theory described the
electronic structure of the atom as the
probability of finding electrons within
certain regions of space.
Today’s atomic model is based on the principles of wave mechanics.
According to the theory of wave mechanics, electrons do not move
about an atom in a definite path, like the planets around the sun.
In the current model of the atom,
electrons occupy regions of space
(orbitals) around the nucleus
determined by their energies.

ATOMIC STRUCTURE
1.10. THE STANDARD MODEL
When scientists study the subatomic particles and forces that bind them together,
they also learn about the early history of the universe and how it began with the
"Big Bang." When the universe was very young, atoms didn't exist, because it was
too hot for them to form. The only form of matter was a sort of "primordial soup,"
consisting of the most basic particles, such as quarks and electrons.
The instruments that particle
physicists use for their studies
include accelerators, detectors and
powerful computers. Accelerators
give the protons enormous energy.
To study very small particles
scientists need very high-energy
protons and very big accelerators.
A particle accelerator uses an electric field to
propel electrically charged particles in a desired
direction.
Activity 1.10.1: Here is a short video: Large Hadron rap

ATOMIC STRUCTURE
Physicists have developed a theory called The Standard Model that
explains what the world is and what holds it together. It is a simple
and comprehensive theory that explains all the hundreds of particles
and complex interactions with only:
The Standard Model describes
how the fundamental particles
affect each other–how they
interact, the forces they feel.

ATOMIC STRUCTURE
While an atom is tiny, the nucleus is ten thousand
times smaller than the atom and the quarks and
electrons are at least ten thousand times smaller than
that. We don't know exactly how small quarks and
electrons are; they are definitely smaller than 10-18
meters, and they might literally be points, but we do
not know.
It is also possible that quarks and electrons are not
fundamental after all, and will turn out to be made up
of other, more fundamental particles.
If the atom was the
size of a stadium, the
nucleus would be the
size of a marble.

ATOMIC STRUCTURE
Dalton’s model
(1803)
Thomson’s plum-pudding
model (1897)
Rutherford’s model
(1909)
Bohr’s model
(1913)
Charge-cloud model
(present)
Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 125
Greek model
(400 B.C.)
1800 1805 ..................... 1895 1900 1905 1910 1915 1920 1925 1930 1935 1940 1945
1803 John Dalton
pictures atoms as
tiny, indestructible
particles, with no
internal structure.
1897 J.J. Thomson, a British
scientist, discovers the electron,
leading to his "plum-pudding"
model. He pictures electrons
embedded in a sphere of
positive electric charge.
1904 Hantaro Nagaoka, a
Japanese physicist, suggests
that an atom has a central
nucleus. Electrons move in
orbits like the rings around Saturn.
1911 New Zealander
Ernest Rutherford states
that an atom has a dense,
positively charged nucleus.
Electrons move randomly in
the space around the nucleus.
1913 In Niels Bohr's
model, the electrons move
in spherical orbits at fixed
distances from the nucleus.
1924 Frenchman Louis
de Broglie proposes that
moving particles like electrons
have some properties of waves.
Within a few years evidence is
collected to support his idea.
1926 Erwin Schrödinger
develops mathematical
equations to describe the
motion of electrons in
atoms. His work leads to
the electron cloud model.
1932 James
Chadwick, a British
physicist, confirms the
existence of neutrons,
which have no charge.
Atomic nuclei contain
neutrons and positively
charged protons.
+
-
-
-
-
-e
e
e
+
+ +
+
++
+
+
e
ee
e
e
ee

ATOMIC STRUCTURE
Activity 2.3.1: Protons, neutrons and
electrons experiences
Challenge
Students have to design an experiment to
understand the process of solving problems by
using indirect evidence fallowing the scientific
method.
Key: Atomic model

ATOMIC STRUCTURE
2. PARTICLES IN THE ATOM
An atom can be identified by two numbers:
• The number of protons in the nucleus of an atom determines an element’s atomic
number (Z). The atomic number of an element never changes, meaning that the
number of protons in the nucleus of every atom in an element that is always the
same.
• All atoms have a mass number (A). It is the sum of the number of protons and
neutrons.

ATOMIC STRUCTURE
2.1. PARTICLES
• Example
– number of protons
– number of neutrons
– number of electrons *
– Atomic number
– Mass number
F19
9
= 9
= 10
= 9
= 9
= 19
+
* In a neutral atom, the number of electrons equals the
number of protons.

ATOMIC STRUCTURE
– number of protons?
– number of neutrons?
– number of electrons?
– Atomic number?
– Mass number?
Br80
35
2.1. PARTICLES

ATOMIC STRUCTURE
However…
– number of protons
– number of neutrons
– number of electrons
– Atomic number
– Mass number
Na23
11
+
Sodium ion
= 11
= 12
= 10
= 11
= 23
 Why?
2.1. PARTICLES

ATOMIC STRUCTURE
2.1. PARTICLES
Electron
Proton
Neutron
Name Symbol Charge
Relative
mass
Actual
mass (g)
e-
p+
no
-1
+1
0
1/1840
1
1
9.11 x 10-28
1.67 x 10-24
1.67 x 10-24

ATOMIC STRUCTURE
2.1. PARTICLES
Activity 2.1.2: Using a periodic table and what you know about
atomic number, mass and electrons, fill in the chart:
Element Symbol Atomic
Number
Atomic
Mass
Protons Neutrons Electrons Charge
8 8 8
Potassium 39 +1
Br 45 -1
30 35 30
Activity 2.1.1: Mass number practice

ATOMIC STRUCTURE
2.2. ISOTOPES
The number of protons for an element must always be the same (e.g.
oxygen always has 8 protons), but the number of neutrons can be different.
Atoms of an element can have different numbers of neutrons in the nucleus,
thus different atomic masses.
Atoms that have the same number of protons, and hence
the same atomic number, but different numbers of
neutrons are called isotopes.

ATOMIC STRUCTURE
2.2. ISOTOPES
Isotopes of Hydrogen

ATOMIC STRUCTURE
2.2. ISOTOPES
The average atomic mass of an element is found by
adding together the product of the mass of the isotope
an percent abundance.
EXAMPLE: Calculate the avg. atomic mass of oxygen if its
abundance in nature is 99.76% 16O, 0.04% 17O, and 0.20% 18O.

ATOMIC STRUCTURE
2.2. ISOTOPES

ATOMIC STRUCTURE
2.2. ISOTOPES
Activity 2.2.1: Find mercury’s average atomic mass if we know:
After, not before! Looking at the average
atomic mass printed on the periodic table.

ATOMIC STRUCTURE
3. PERIODIC TABLE
Activity 3.1: Click on this link and explore the Periodic
table of the elements.
Activity 3.2: Click on each Elements to know.
Activity 3.3: Sing Slow “The new periodic table song”

ATOMIC STRUCTURE
1.3. HISTORY OF THE PERIODIC TABLE
The early versions of the periodic table included
approximately 60 known elements, while our current version
includes 118.
One of the major developments that allowed for what
became known as the periodic table was the idea of atomic
mass, which is attributed to John Dalton.

ATOMIC STRUCTURE
An early version of the periodic table was first published by
Julius Lothar Meyer in 1864, where he used the concept of
valence to group similar elements together.
In 1865, Newlands described a periodic pattern in the
properties of the elements that he referred to as the Law of
Octaves. This anticipated later developments in our
understanding of the periodic law.
Newlands' Law of Octaves Octaves
H Li Ga B C N O
F Na Mg Al Si P S
Cl K Ca Cr Ti Mn Fe
Co, Ni Cu Zn Y In As Se
Br Rb Sr Ce, La Zr Di, Mo Ro, Ru
Pd Ag Cd U Sn Sb Te
I Cs Ba, V Ta W Nb Au
Pt, Ir Tl Pb Th Hg Bi Th

ATOMIC STRUCTURE
Between 1869 and 1871, Russian chemist Dmitri Mendeleev
systematically arranged 60 elements based on increasing
atomic weight.

ATOMIC STRUCTURE
Mendeleev’s table became widely accepted, primarily
because he predicted the characteristics and placement of
elements which were yet to be discovered.
Activity 1.3.1: Here is a short video: A brief history of the
periodic table
Activity 1.3.2: Video: GCSE Science Revision - The Periodic
Table of the elements
Activity 1.3.3: Here is a movie: Chem KS3 BBC Bitesize Old 04
The Periodic Table

ATOMIC STRUCTURE
In 1913, English physicist Henry Moseley (1887-1915) examined the x-
ray spectra of a number of chemical elements. His results led to the
definition of atomic number as the number of protons contained in
the nucleus of each atom. He then realized that the elements of the
periodic table should be arranged in order of increasing atomic
number instead of increasing atomic mass.
When ordered by atomic number, the discrepancies within
Mendeleev’s table disappeared.
The result is the periodic table as we know it today.

ATOMIC STRUCTURE
3.2. ELECTRON CONFIGURATION
Electron configuration of an element is the
arrangement of its electrons in its atomic orbitals
One can obtain and explain a great deal of the
chemistry of the element by knowing its electron
configuration

ATOMIC STRUCTURE
Aufbau Principle: Electrons are added one at a time to the lowest
energy orbitals available until all the electrons of the atom
have been accounted for.
Pauli Exclusion Principle: An orbital can hold a maximum of two electrons.
To occupy the same orbital, two electrons must spin in opposite
directions.
Hund’s Rule: Electrons occupy equal-energy orbitals so that a maximum
number of unpaired electrons results.
Within a sublevel, place one electron per orbital before pairing them.
“Empty Bus Seat Rule”
FILLING RULES FOR ELECTRON ORBITALS

ATOMIC STRUCTURE
Order in which subshells are filled with electrons

ATOMIC STRUCTURE
Notation
• Orbital Diagram
• Electron Configuration

ATOMIC STRUCTURE
Notation
• Longhand Configuration
• Shorthand Configuration

ATOMIC STRUCTURE
3.3. PERIODIC PATTERNS

ATOMIC STRUCTURE
3.4. ELEMENTS IN THE HUMAN BODY: TOP TEN

ATOMIC STRUCTURE
3.5. TRENDS IN THE PERIODIC TABLE
In this section, we are going to look at specific properties that can
be predicted by an element's position on the periodic table.
Ionization energy is the energy required to remove an electron
from a specific atom.
Ionization energy generally increases as you move left to right
across the table or from bottom to top.

ATOMIC STRUCTURE
Electron affinity is the energy required for an electron to be added to a
neutral atom in its gaseous form. Because most atoms release energy
when an electron is added, most electron affinity values are negative.
These values generally become more negative (more energy is released) as
you move left to right across the table or from bottom to top.
Electron affinities (in kJ/mol) for representative elements in the first five periods. Electron affinities are
written as negative numbers because energy is being released.

ATOMIC STRUCTURE
One important
characteristic that
determines the way in
which elements behave is
the total size of each
atom. Free atoms are
spherical in shape, so the
relative sizes of the
elements can be
compared by looking at
each atom's atomic
radius, which is the
distance from an atom's
nucleus to the electrons
in the outermost orbitals.

Atomic and ionic radii of the first five elements in Groups 1, 2, 13, 16, and 17. Atoms are shown in gray.
The most common ion for each element is shown in either green (for cations) or purple (for anions).
ATOMIC STRUCTURE
Ionic radius helps
to indicate the size
of an ion as
compared to its
parent atom.
Cations always
have a smaller
atomic radius than
the parent atom;
anions always have
a larger atomic
radius than the
parent atom.

ATOMIC STRUCTURE
Electronegativity is a measure of the relative tendency of an atom to
attract electrons to itself when chemically combined with another atom.
In general, electronegativity increases as you move left to right across the
table and from bottom to top.
The electronegativity scale was developed by Nobel Prize winning American chemist Linus Pauling. The
largest electronegativity (3.98) is assigned to fluorine, and all other electronegativity measurements are
made relative to that value.

Summary of periodic trends within periods and groups.
ATOMIC STRUCTURE
Periodic trends in metallic and non-metallic characteristics mirror
those of the other properties that we have discussed; the most
metallic elements are at the lower left of the table, and the most non-
metallic elements are at the upper right.

ATOMIC STRUCTURE
Activity 3.5.1: Write the electron configurations for the following
ions:
a. Li+
b. Be2+
c. N3-
d. O2-
e. F-
Activity 3.5.2: Which configuration corresponds to an atom with a
larger radius: 1s22s22p1 or 1s22s22p6? Identify these elements.
Activity 3.5.3: Which configuration corresponds to an atom with a
larger radius: 1s22s22p6 or 1s22s22p63s23p6? Identify these
elements.

ATOMIC STRUCTURE
Activity 3.5.4: Using only the periodic table, arrange each set of atoms in order
of increasing atomic radius:
a. Rb, Cs, Li
b. B, Li, F
c. Cl, F, Ba
d. Rb, Be, K
Activity 3.5.5: Arrange each set of atoms and ions in order of increasing radius:
a. O, O-, O2-
b. Li+, Li, Be2+
c. Na+, Mg2+, Al3+
d. F-, Br-, O2-
Activity 3.5.6: Arrange each set of atoms in order of increasing electron affinity
(least negative to most negative):
a. Li, K, F
b. F, O, N
c. S, Cl, Ca

ATOMIC STRUCTURE
BIBLIOGRAPHY
- https://www.youtube.com/watch?v=WLUmuYkxExQ
- https://www.youtube.com/watch?v=TICGU0Qq1h0
- https://www.youtube.com/watch?v=OGUOmV33P9I
- https://www.youtube.com/watch?v=HnmEI94URK8
- https://www.youtube.com/watch?v=j50ZssEojtM
VIDEOS

ATOMIC STRUCTURE
BIBLIOGRAPHY
- http://mypages.iit.edu/~smile/ch8706.html
- http://www.unit5.org/Page/4023
- http://www-outreach.phy.cam.ac.uk/camphy/nucleus/nucleus1_1.htm
- http://www.unit5.org/Page/51
- http://www.daviddarling.info/encyclopedia/R/Rutherfords_experiment_
and_atomic_model.html
- http://www.chemheritage.org/discover/online-resources/chemistry-in-
history/themes/atomic-and-nuclear-structure/thomson.aspx
- http://www.physicsoftheuniverse.com/scientists_rutherford.html
- http://www.teach-nology.com/gold/atom1.html
- http://ap-physics.david-s.org/geiger-marsden-experiment/
- https://www.learner.org/courses/physics/unit/text.html?unit=1&secNu
m=2
- http://www.learner.org/vod/vod_window.html?pid=798
- http://www-outreach.phy.cam.ac.uk/camphy/neutron/neutron5_1.htm
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