Formation of compounds Universal Solvents, Edible Rocks,

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Formation of compoundsUniversal Solvents, Edible
Rocks, Global Warming
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Salt The rock we eat

• Sources Rock salt, Sea salt
• One of the basic tastes
• Preservative
• Once rare Roman soldiers paid in salt
• That guy isnt worth his salt
• White Gold
• Road Melt
• What is better
• than sodium chloride?

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Properties of Salt

• Cube
• Brittle
• Melts _at_ 800 degrees
• Dissolves in water
• Solution conducts electricity
• Chemically it doesnt do much. Salt will sit in
  a salt shaker for years not change. Why?

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Sodium vs. Chloride

• Shiny metal
• Violently reacts with water
• Always combines with something else

• Pale green poisonous gas
• Used in WWI
• Disinfectant
• Very reactive

When these two elements combine they form safe
stable old table salt. Why?
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Carbon Dioxide
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CO2

• Colorless gas
• Combustion of Organic materials
• Cellular respriation
• Industry
• At -80 it solidifies into dry ice
• Soluable in water soda pop

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Carbon vs Oxygen

• Non-metal
• Unreactive until you raise the temperature
• Basis of life Organic Chemistry

• Non-Metal
• Colorless, odorless, tasteless
• Soluable in water
• Causes rusting
• Metabolic waste of plants microbes
• They changed the Earths atmosphere

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Greenhouse effect

• Like any stone the Earth heats up in the
  sunlight, and then heat escapes in the dark
• Carbon Dioxide water vapor insulates the Earth
  reflecting escaping heat back
• Burning fossil fuels leads to an increase of CO2
  levels rise warming the globe
• Melting the ice caps?

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Water

• The biological medium
• ¾ of the planet is covered in water
• 1 of the planets water is potable
• Only substance thats found in all three states
  of matter
• Polar molecule
• Positive side
• Negative side

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Special properties of water

• Cohesion water sticks to itself
• Adhesion water sticks to other things
• Surface tension cohesion at the surface
• High specific heat It takes a lot of energy to
  heat water
• Water heats and cool slowly
• Solid form is less dense than liquid
• Universal solvent water
• can dissolve many many things

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Oxygen vs. Hydrogen

• Lightest element
• Most abundant
• Reactive element
• Burns easily
• Freezes at -253 degrees

• Non-Metal
• Colorless, odorless, tasteless
• Soluable in water
• Causes rusting
• Metabolic waste of plants microbes
• They changed the Earths atmosphere

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Hindenburg disaster

• Dirigible caught fire and burned in less than a
  minute
• 37 killed
• Burning wreck fell onto ground crew

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NaCl CO2 H2O

• These compounds have very different properties
  than the elements that make them up.
• Next well examine the types of bonds that form
  molecules
• Ionic Covalent

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Octet Rule

• Noble gases are stable because they have just the
  right number of valence electrons.
• 2 for helium
• 8 for the rest
• This balances them eneregetically
• Octet Rule all elements try to form bonds so
  they have 8 valence electrons
• Some try to have just 2

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Ions

• When an atom gains or loses an electron it takes
  on a negative or positive charge
• If you gain an electron (negative energy) you
  have a negative charge Anion
• Plus a negative is subtraction
• Cl-
• If you lose an electron (negative energy) you
  have a positive charge Cation
• Minus a negative is addition
• Na

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Electrons can be transferred

• Sodium has 1 valence electron
• Chlorine has 7 valence electrons
• How can Chlorine achieve the octet?
• It gained an electron giving it a negative charge
• It resembles a noble gas
• Did Sodium achieve the octet?
• It now resembles neon

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Magnesium Oxide

• Another example, magnesium and oxygen.
• The magnesium would lose two electrons, becoming
  2 charged and the oxygen would gain the two
  electrons becoming -2 charged in the process.
• The positive/negative charge attraction (this
  time 2/-2, would hold
• the two ions together.
• Formula MgO

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Magnesium Chloride

• Last example, Mg and Cl.
• The magnesium would lose two electrons, becoming
  2 charged and two chlorines (not one) would each
  gain one electron, each becoming -1 charged in
  the process.
• The three ions would adhere (bond) to each other
  by the positive/negative attraction between the
  ions.
• Formula MgCl2

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3 points

• All transition metals and rare earth metals act
  as positives in ionic bonding.
• Hydrogen can be involved in ionic bonding. It
  will act as a nonmetal with a -1 charge. It is
  named hydride. Symbol H-
• There are more complex ionic bonding situations
  which will remain for later. For example, the
  bond between NH 4 and Cl in ammonium chloride
  is an ionic bond.

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The periodic table organizes charge Metal ions

• 1A forms 1 cations Na, Li, K
• 2A forms 2 cations Be2 , Mg2 , Ca2
• 3A forms 3 cations Al3
• The name of these is the same as the name of the
  element.
• Example Na is called the sodium cation
• Notice that we dont write the 1s, it is assumed

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The periodic table organizes charge Non metal
ions

• 5A forms -3 anions N3-, P3-
• 6A forms -2 anions O2-, S2-
• 7A forms -1 anions F-, Cl-, Br-, I-
• The name of anions end in ide
• Example Br- is called the bromide ion

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Practice problems

• Write the symbol and name of the ion formed when
• Strontium loses two electrons
• An Iodine atom gains one electron
• A sulfur atom gains two electrons
• An aluminum atom loses three electrons
• A calcium atom loses two electrons
• How many electrons are lost or gained in the
  forming of each ion?
• 6. Ba2
• As3-
• Cu2

• What do you mean I have to practice?

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Solutions

• Make a plan
• An atom that loses electrons forms a positively
  charged ion (cation)
• An atom that gains electrons forma a negatively
  charged ion (anion)
• Sr2 Strontium ion
• I- Iodide ion
• S2- Sulfide ion
• Al3 Aluminum ion

• 5. Ca2Calcium ion
• 6. 2 lost
• 7. 3 gained
• 8. 2 lost

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Ions attract each other

• Opposites attract
• Ionic bonds between ions, they are trading
  electrons.
• Ionic compounds have ionic bonds
• Crystals form
• Stable so they have high melting points
• Dont bend
• Shatter

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Electrons can be shared Covalent Bonds

• H2O is not ionic like NaCl
• It becomes stable like noble gases in a different
  way.
• In water the Hs and O share electrons
• Its a different kind of attraction

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Covalent bonds

• Covalent compounds have covalent bonds
• 1 unit of a covalent compound is called a
  molecule
• Sometimes they are called molecular compounds
• They have lower melting points
• Examples Water, Carbon Dioxide, Sugar, Gasoline,
  Wax, Lighter fluid, propane

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Now go practice, all night long