Periodic table e
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Transcript of Periodic table e
History of the Periodic TableAristotle’s Classical Elements
Earth: • Cold and dry • Solids Water: • Cold and wet • Liquids
Air: • Hot and wet • Gases Fire: • Hot and dry • Plasma &
heat Aether: • Heavenly Bodies
History of the Periodic TableAntoine Laurent Lavoisier
Wrote the first chemistry textbook• 1789• Elementery Treatise of
Chemistry Contained a list of 33
elements• Included caloric and
light
History of the Periodic TableJohann Wolfgang Döbereiner
Formulated the law of triads• 1828• Grouped the elements
in groups of three with the same properties
• Br, Cl and I• Ca, Ba, Sr
History of the Periodic TableAlexandre-Emile de Chancortois
1862 Wrote the elements on a piece
of ribbon Ordered elements by atomic
weight Rolled ribbon into a cylinder with
16 units circumference Noticed that elements with
similar properties were aligned vertically
Called it the “telluric helix”
History of the Periodic TableAlexandre-Emile de ChancortoisModern day Telluric Helix: Alexandre Arrangement
History of the Periodic TableJohn Newlands
Formulated the Law of Octaves• 1863• Ordered elements by atomic
weight• Noticed that properties repeated
every 8 elements
History of the Periodic TableJohn Newlands
Law of octaves fail beyond Calcium• Why?
John Newlands was told that his arrangement was as arbitrary as arranging the elements alphabetically
and his paper was rejected for publication
History of the Periodic TableDmitri Mendeleev
Published the first version of the periodic table• 1869• Contained 56 elements
arranged according to atomic masses
• Predicted the existence and properties of unknown elements
Formulated the periodic law
History of the Periodic TableDmitri Mendeleev
“I saw in a dream a table where all the elements fell into place as required. Awakening, I immediately
wrote it down on a piece of paper” – Dimitri Mendeleev
History of the Periodic TableProblems with Mendeleev’s Table
Sb51
121,76
Te52
127,60
I53
126,91
Ar18
39,95
K19
39,10
Ca20
40,08
“Corrected” the atomic weights if it caused the element to be placed in the wrong group• Assumed that weights
were determined incorrectly due to lack of technology
History of the Periodic TableMendeleev’s Predictions
Property Eka-aluminium GalliumAtomic mass 68 69.72
Density (g/cm³) 6.0 5.904Melting Point (°C) Low 29.78
Oxide's Formula
Ea2O3 (density: 5.5 g/cm³)
(soluble in both alkalis and acids)
Ga2O3 (density: 5.88 g/cm³)
(soluble in both alkalis and acids)
Chloride's Formula Ea2Cl6 (volatile) Ga2Cl6 (volatile)
History of the Periodic TableHenry Mosely
Recognised relationship between x-ray wavelength and nuclear charge• 1914• Rearranged elements
according to nuclear charge• Showed gaps in Mendeleev’s
table at atomic numbers 43 and 6
Also predicted new elements
History of the Periodic TableHenry Mosely
Was sent to serve as foot soldier in WWI before his research was finished
Was killed by a snipers bullet
Britain now assign non-combat duties to their scientists during war time
History of the Periodic TableGlenn T. Seaborg
Co-discovered 10 new elements
In 1944 he moved the actanoids out of the main body of the periodic table to its current position
History of the Periodic TableGlenn T. Seaborg
“This is the greatest honour ever bestowed
upon me – greater even, I think, than winning the
Nobel Prize.” – Glenn T. Seaborg
Periodic TableStructure
Horizontal Rows:• Periods• Chemical properties vary across
the periods• Each Period represents a new
energy level
Periodic TableStructure
I
Group I:• Alkali Metals• React violently with water to
form an alkaline solution• Have one valence electron• Valence = 1
Periodic TableStructure
Group II:• Alkaline earth Metals• React violently with water to
form an alkaline solution• Occur abundantly in the earths
crust• Have two valence electrons• Valence = 2
III
Periodic TableStructure
Transition metals:• Elements with an
incomplete d-subshell
• Can form cations with incomplete d-subshells
Periodic TableStructure
Group VI:• Chalcogens• S, Se and Te are commonly
found in copper ore• Has six valence electrons• Valene = 2
I
II III IV V VI
Periodic TableStructure
Group VII:• Halogens• React with metals to form
salts• Has seven valence electrons• Valence = 1
I
II III IV V VIVII
Periodic TableStructure
Group VIII:• Noble Gasses• Rare and Inert• Have eight valence electrons• Valence = 0
I
II III IV V VIVII
VIII
Lanthanides:• Rare earth elements• Form cations with charge +3
I
II III IV V VIVII
VIII
Periodic TableStructure
PeriodicityDefinition
The chemical and physical properties of elements• Change from left to right across a period • Change from top to bottom in a group• Similarities between the properties of elements in
the same group Periodicity:
• The periodic variation in the properties of elements as one moves from left to right and from top to bottom in the periodic table
Atom radius
Increase
Decrease from left to right (increase from right to left)
Increase from top to bottom
Periodicity
Atom radius: DefinitionThe distance between the nucleus and the outer most stable orbital
Periodicity
Atom radius: Left to Right Decrease from left to right
• Atom number increase• Number of protons, and therefore the nucleus
charge, increase• Electrons are added to the same principal energy
level• Electrons are more strongly attracted to the
nucleus
3p+
e-
5p+e-
e-
e-4p+e-
e-
Periodicity
Atom radius: Top to Bottom Increase from top to bottom
• A new energy level is added• The outer electrons are further away from the
nucleus• Inner electrons shield the outer electrons from
the nucleus (screening effect)• Electrons are attracted by the nucleus less
strongly• Atom radius decrease
Periodicity
Screening Effect
12p+e- e- e-
e-e-
e-
e-e-
e-e-
e-e-
e-
e-
Outer e- attracted by nucleus
Outer e- repelled by inner e-
Experience a smaller net attractive force
Inner e- “shields” outer e- from nucleus
Periodicity
PeriodicityIonization energy
The energy required to remove an electron from an atom
12p+e- e- e-
e-e-
e-
e-e-
e-e-
e-
e-
MgMg+
PeriodicityIonization energy: Left to right Increase from left to right
• Atom number increase• Number of protons, and therefore the nucleus
charge, increase• Electrons are added to the same principal energy
level• Electrons are more strongly attracted to the
nucleus• More energy required to remove electrons
PeriodicityIonization energy: Top to Bottom Decrease from top to bottom
• A new energy level is added• The outer electrons are further away from the
nucleus• Inner electrons shield the outer electrons from
the nucleus (screening effect)• Electrons are attracted by the nucleus less
strongly• Less energey required to remove electron
Borons ionization energy is less than that of Beryllium• Be: S-orbital completely filled• B: A single electron in the p-orbital• Electrons in the p-orbital has more energy than
elcetrons in s-ornitals• Less energy required to remove electron
PeriodicityIonization Energy: Deviations
Oxygen has a lower ionization energy than Nitrogen• N: One electron in each p-orbital• O: The first p-orbital contains an electron pair• Electrons in the same orbital repel eachother• Less energy required to remove electron
PeriodicityIonization energy: Deviations