The Periodic Table of Elements

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The Periodic Table of Elements
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How Did the Periodic Table Get Organized?

• In the early 1860s, scientists knew some of the
  properties of over 60 elements, but there was no
  organization for these elements.
• Once the elements were organized, scientists
  could look at their properties and figure out how
  they interact with each other.

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Dmitri Mendeleev

• Russian chemist who first discovered a pattern to
  the elements in 1869.
• In order to try and organize the elements,
  Mendeleev wrote the names of the elements along
  with their properties on cards.
• He then arranged the cards by different
  properties such as density,
• appearance, and melting point.

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Classes of Elements

• Elements are classified into 3 categories
• Metals
• Non-metals
• Metalloids

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Metals

• Most elements are metal
• Metals are found to the left of the zigzag line
  on the periodic table.
• Most metals are solid at room temperature
• Properties of metals
• Shiny
• Ductile (can be drawn into thin wires)
• Malleable (can be shaped without shattering)
• Good conductors of thermal energy

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Nonmetals

• Found to the right of the zigzag line on the
  periodic table.
• More than half of the nonmetals are gases at room
  temperature.
• Properties of nonmetals opposite of metals

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Metalloids

• Also called semiconductors
• Metalloids are the elements that border the
  zigzag line on the periodic table.
• Properties of metalloids some properties of
  metals, and some properties of nonmetals.
• Ex. Tellurium is shiny but brittle, so it can
  not be shaped.

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How to Read the Periodic Table

• Each element is identified by a chemical symbol
• Each square on the table includes
• The elements name (some are named after
  scientists, some after places)
• Chemical symbol in Latin (First letter is
  capitalized, second letter is lowercase)
• Atomic number (number of protons in the atom)
• Atomic Mass (approximate number of protons and
  neutrons in the nucleus)
• How to find the number
• of protons and neutrons
• (atomic mass atomic number)

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Periods

• Rows in the periodic table are called periods
• Physical and chemical properties change gradually
  from left to right (go from metal, to metalloid,
  to nonmetal)
• Reactivity changes from left to right (most
  reactive to least reactive)

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Groups

• Each vertical column is called a group
• Elements in the same group often have similar
  chemical and physical properties.

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Group 1 Alkali Metals

• The most reactive metals in the periodic table.
• Often stored in oil to prevent them from
• reacting with water and oxygen in the air.
• Shared properties softness, color of silver,
• shininess, low density

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Group 2 Alkaline Earth Metals

• A little less reactive than alkali metals.
• Group 2 elements have many uses.
• Ex. Calcium is needed to keep your teeth and
  bones strong. Calcium is also found in cement
  and chalk.
• Shared properties color of silver, higher
  densities than alkali metals.

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Groups 3-12 Transition Metals

• Shared properties shininess, good conductors of
  thermal energy and electric current, higher
  densities and melting points.

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Groups 3-12 Transition Metals

• Why are some transition metals at the bottom of
  the table?
• Elements in the first row are called lanthanides.
  
• Shiny
• Reactive
• Metals
• Elements in the second row are called actinides.
  
• Atoms of actinides are radioactive and unstable.
  
• Can change into the atoms of other elements.
• Made in laboratories.

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Group 17 Halogens

• Halogens bond with metals to form salts.
• Shared Properties poor conductors of
  electricity, violent reactions with alkali metals
  to form salts.

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Group 18 Noble Gases

• The most un-reactive elements on the table.
• They will not bond with anything else.

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Hydrogen

• The properties of Hydrogen are so different from
  the other groups that it is placed all by itself.
• Hydrogen is placed above the alkali metals
  because it is very reactive. However, Hydrogen
  is most like nonmetals.