Reactivity of Atoms Based on Their Placement in The Periodic Table
*Click the link below and check out the losers, takers, and kings analogy of the periodic table of elements!
http://www.mansfieldct.org/schools/mms/staff/hand/chemkingoctet06.htm
And the "Elements Song"
http://www.privatehand.com/flash/elements.html
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The Periodic Law
Mendeleev developed his periodic table before the discovery of protons. He did not know that two elements could not have the same number of protons.
Key Concept: In the modern periodic table, elements are arranged by increasing atomic number (number of protons)
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Periods
Each row in the table of elements is a period
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The number of elements per period varies because the number of orbitals increases from energy level to energy level
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Groups
Each column on the periodic table is called a group (sometimes called a family)
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Key Concept: Properties of elements repeat in a predictable way when atomic numbers are used to arrange elements into groups.
The elements in a group have similar electron configurations. An element's electron configuration determines it's chemical properties
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What do you call a joke that is based on cobalt, radon, and yttrium?
CoRnY !!!!!
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Atomic Mass Unit
Because the mass of an atom is extremely small, scientists created the atomic mass unit.
How?
Scientists assigned 12 atomic mass units to carbon­ 12 which has 6 protons and 6 neutrons.
An atomic mass unit (amu) is defined as one twelfth the mass of carbon­ 12 atom
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Atomic Mass
The atomic mass of chlorine is 35.453. How was this calculated?
There are two natural isotopes of chlorine, chlorine­35 (17p+ and 18n) and chlorine­ 37 (17p+ and 20n)
35.453 is a weighted average because the percentage of Cl­35 that is found in nature is 75.78% and percentage of Cl­37 is 24.22%
So.... if you multiply those occurrences with their masses, add them together, and divide by 2 to get the mass of 35.453)
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Classes of Elements
Elements can be classified as solids, liquids, or gasses based on their states at room temperature.
• Solids
• Liquids
• gases
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Classes of Elements Elements are also classified based on whether the occur naturally or not
Elements that do not occur naturally have an atomic number greater than 92
Check them out....
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Metals
The majority of elements are classified as metal:
Metals are:
• good conductors of electric current and heat
• solid at room temperature (except Mercury)
• most are malleable
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Transitional Metals
Metals in groups 3­12 are called the transition metals
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Nonmetals
Poor conductors of heat and electricity
Many are gasses at room temperature
Some are very reactive, some are not
Example: Fluorine is the most reactive nonmental
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Metalloids
Properties fall between metals and nonmetals
Example: Metalloid's ability to conduct electric current varies with temperature
Example: Silicon (Si) is a poor conductor at room temperature but a good conductor at high temperatures 15
Variation Across a Period
Key Concept: Across a period from left to right, the elements become less metallic and more nonmetallic in their properties
The most reactive metals are on the left of the periodic table and the most reactive nonmetals are on the right in group 17
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