discovering a pattern dmitri mendeleev- russian chemist- discovered a pattern to the element in 1869...
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Discovering a PatternDiscovering a Pattern
Dmitri Mendeleev- Russian Chemist- Dmitri Mendeleev- Russian Chemist- discovered a pattern to the element in discovered a pattern to the element in 18691869
First he arranged them by different First he arranged them by different properties (density, appearance, MP).properties (density, appearance, MP).
After much thought he arranged them in After much thought he arranged them in order of increasing atomic mass.order of increasing atomic mass.
When he did that a pattern appeared!!!!When he did that a pattern appeared!!!!
Periodic Properties of the Periodic Properties of the ElementsElements
When arranged in order of increasing When arranged in order of increasing atomic mass, those that had similar atomic mass, those that had similar properties occurred in a repeating properties occurred in a repeating pattern.pattern.
Periodic-happening at regular Periodic-happening at regular intervalsintervals
Mendeleev found that the elements Mendeleev found that the elements properties followed a pattern that properties followed a pattern that repeated every 7 elements.repeated every 7 elements.
Predicting Properties of Missing Predicting Properties of Missing ElementsElements
• Mendeleev predicted that elements Mendeleev predicted that elements yet to be found would fill in the gaps yet to be found would fill in the gaps of the patternof the pattern
• He used the pattern to predict their He used the pattern to predict their propertiesproperties
• By 1886 all the gaps had been filled By 1886 all the gaps had been filled and his predictions were correct!and his predictions were correct!
Changing the ArrangementChanging the Arrangement
A few elements did not fit the pattern in A few elements did not fit the pattern in Mendeleev’s tableMendeleev’s table
Mendeleev thought if he found a more accurate Mendeleev thought if he found a more accurate atomic mass than he would fix the flaws in his atomic mass than he would fix the flaws in his table. But his masses were correct. table. But his masses were correct.
Henry Moseley-determined the # of protons-the Henry Moseley-determined the # of protons-the atomic #-atomic #-
All elements fit the pattern in the table when All elements fit the pattern in the table when arranged buy atomic #.arranged buy atomic #.
Periodic Law- repeating chem. & phys. Properties Periodic Law- repeating chem. & phys. Properties of elements change periodically with the of elements change periodically with the elements atomic #elements atomic #
MetalsMetals
1.1. Most ElementsMost Elements
2.2. Found LEFT of the zigzag line on the tableFound LEFT of the zigzag line on the table
3.3. Few electrons in their outer energy levelFew electrons in their outer energy level
4.4. Most are solid at room temp. Mercury is an exception-It is Most are solid at room temp. Mercury is an exception-It is liquid at room temp.liquid at room temp.
5.5. ShinyShiny
6.6. Ductile-drawn into thin wiresDuctile-drawn into thin wires
7.7. Good conductors of electric currentGood conductors of electric current
8.8. Good conductors of thermal energyGood conductors of thermal energy
9.9. Malleable- flattened with a hammer and won’t shatterMalleable- flattened with a hammer and won’t shatter
NonmetalsNonmetals Found right of the zigzag line on the tableFound right of the zigzag line on the table Almost a complete set of electrons in their outer Almost a complete set of electrons in their outer
level.level. Atoms of the elements in Group 18 (noble gases)-Atoms of the elements in Group 18 (noble gases)-
have a complete set of electronshave a complete set of electrons More than ½ are gases at room temp.More than ½ are gases at room temp. Many properties of nonmetals are opposite of Many properties of nonmetals are opposite of
metal propertiesmetal properties Not malleable or ductile, not shiny, poor Not malleable or ductile, not shiny, poor
conductors of thermal energy and electric currentconductors of thermal energy and electric current
MetalloidsMetalloids
Can also be called Can also be called semiconductors.semiconductors. These border the zigzag line on the table.These border the zigzag line on the table. About ½ have a complete set of electrons in About ½ have a complete set of electrons in
their outer energy leveltheir outer energy level Have properties of both metals and Have properties of both metals and
nonmetalsnonmetals Ex: Tellurium is shiny BUT it is brittleEx: Tellurium is shiny BUT it is brittle Ex: Boron-very hard but also very brittle, at Ex: Boron-very hard but also very brittle, at
high temps. It is a good conductor of high temps. It is a good conductor of electric currentelectric current
Chemical SymbolsChemical Symbols
Each element is identified by a chemical Each element is identified by a chemical symbol. Symbols are worldwide.symbol. Symbols are worldwide.
Some elements are named after Some elements are named after scientists, some are named after places. scientists, some are named after places. Some names may vary by country. Some names may vary by country.
One or two letters. The first letter is One or two letters. The first letter is always capitalized.always capitalized.
Newest elements have temporary three Newest elements have temporary three letter symbolsletter symbols
Rows And ColumnsRows And Columns
• Horizontal rows (from left to right) are called PERIODS
• Physical and Chemical Properties in a row follow a periodic pattern as you move across.
• Conductivity and reactivity change gradually as you move left to right
Rows And ColumnsRows And Columns
Vertical columns (top to bottom) are Vertical columns (top to bottom) are called called GROUPSGROUPS
Elements in the same group often Elements in the same group often have similar chemical and physical have similar chemical and physical properties.properties.
A group is also called a A group is also called a FAMILYFAMILY