Periodic Table Blog

History Timeline

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Organization of the Periodic Table

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How is the Periodic Table Organized?

Dmitri Ivanovich Mendeleev wrote a textbook that would be the bases for modern chemical and physical theory. Elements are arranged on the periodic table according to their atomic numbers. The structure of the table displays the specific electron arrangements in each type of atom. The table is divided into vertical columns called groups (families) and horizontal rows called periods. Every element has a period, however only the outer elements (s1, s2, p) are in groups. Hydrogen and helium are special elements, hydrogen usually has a missing or extra electron while helium can only have 2 electrons on the its outer shell. The periodic table is also described as “the grid”. The scientist placed the elements in specific places the way they act and look. When the development of quantum mechanics in the 1920s scientists worked out how the electrons arrange themselves to give the element its properties.

Periodic Meanings

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Periodic Table : Meanings of Phrases

Atomic Radius is atomic size of an atom, preferably meaning the distance from the nucleus of an atom to valence electrons.

Ionization Energy means the energy an atom takes to remove an electron from it completely. This energy increases throughout the periodic table starting left and working its way right.

Electronegavity is the ability in an atom to lure another atom’s electrons to it; which creates a bond between the two atoms. The strength increases across a period, but going down a group, it decreases.

Electron Affinity is the change in energy when an atom adds an electron. Positive or negative affinity is determined by whether the atom becomes more or less stable when gaining the electron. This concept is directly related to the atom’s potential energy either increasing or decreasing.

How Ideas are Represented

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Atomic Radius is represented on the periodic table by seeing the elements from left to right, and realizing that the electrons are placed specifically one by one in order to the outer energy shell. The attraction to protons inside an energy shell is so strong that electrons cannot shield one another. The number of protons is also growing, so the nuclear charge grows when moving along a period. Consequently, the atomic radius decreases. On the contrary, going down a group, the electron number grows. The valence electron number will stay exactly the same. The electrons most vulnerable to the effective the nuclear charge are the outermost ones. The atomic radii will grow when electrons are further away from the nucleus, causing the energy shell to increase.

Ionization Energy is represented in to ways first ionization and second ionization. Second ionization increases in energy much more than first ionization if successful. The energy increases if moving across a period from left to right. But if going down a group, the energy decreases.

Electronegavity is electrons bonding in an atom. If the nuclei does not give off a strong attractive bond on electrons, then the electrons containing low ionization energies will have a low electronegavity. High ionization energy elements have high electronegavities because the nuclei pull strongly on the electrons. If the atomic number increases, the electronegavity will decrease in a group. That is caused by the distance between the nucleus and the valence electron being increased.

Electron affinity is how an atom takes in a new electron. Certain groups in the periodic table are categorized with low electron affinities together. Example: alkaline earths. The stability of an element is determined by what the sub shell is filled with. Most of the groups have low electron affinities. Some elements even have zero or near zero affinities because its stability does not require another electron.

Below is a helpful Chart I found on the website listen in the Bibliography.
“Summary of Periodic Table Trends”
Moving Left --> Right
Atomic Radius Decreases
Ionization Energy Increases
Electronegativity Increases

Moving Top --> Bottom
Atomic Radius Increases
Ionization Energy Decreases

The Anatomy of the Table

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Alkali metals, Alkaline earth metals, Transition metals , Noble Gases-

Transition Metals
· Transition metals are classified by their orbitals or their shells.
· Able to have 32 electrons in their second to last shell. No shell can have more than 32 electrons.
· Transition metals use the outer shells to bond with other elements
· They are located on the “D” block on the periodic table.

Alkali Metals
· Alkali Metals are located in group 1 on the periodic table.
· They are highly reactive and almost never found in nature.
· Contain one electron in their most outer shell.

Alkaline Earth Metals
· Alkaline Earth Metals are located in group 2 on the periodic table.
· React with halogens to form ionic salts.
· Alkaline Earth Metals have two electrons in their valence shell.

Noble Gases
· Noble gases are located in group 8 on the periodic table.
· Noble gases have similar properties; odorless, colorless and have a low chemical reactivity.

Investigation of Properties

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Reactivity, Electron Configuration, & Valence electrons:

· Valence electrons-The electrons in the last energy level in an atom.
· Increase in number as you go across the period but starts back at one when you go to a new period. So the valence electrons stay the same as you go up or down but increase from left to right.
· Reactivity- The reactivity is based on the position of the elements on the periodic table. It depends on how far down the

Electron Configuration

· The electron configuration is the specific way to locate elements on the periodic table by classifying it by the amount of electrons.

Bibliography

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History- unknown, unknown (1997). A BRIEF HISTORY OF THE DEVELOPMENT OF PERIODIC TABLE . Retrieved September 14, 2008, from WOU Web site: http://www.wou.edu/las/physci/ch412/perhist.htm

Organization- Unknown, Unknown The Periodic Table of Elements. Retrieved September 14, 2008, from Maria Curie and the Science of Radioactivity Web site: http://www.aip.org/history/curie/periodic.htm

Meanings- unknown, unknown Organic Atomic Structure. Retrieved September 14, 2008, from Spark Notes Web site: http://www.sparknotes.com/chemistry/fundamentals/atomicstructure/section3.rhtml

Ideas- Helmenstiene , A Periodic Properties of the Elements. Retrieved September 14, 2008, from About Web site: http://chemistry.about.com/od/periodictableelements/a/periodictrends.htm

Properties and Anatomy- Winter, M The Periodic Table. Retrieved September 14, 2008, from WebElements Web site: http://www.webelements.com/