Elements to Compounds

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Elements to Compounds

• NCSCOS 4.02

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Big Picture

• Elements are pure substances with only ONE type
  of atom.
• Most matter is a combination of elements
• Atoms ? elements ? molecules ? compounds
• Vocab terms compound, molecule, chemical
  formula, subscript, ionic bond, covalent bond

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2.1D ELEMENTS combine to form Compounds

• 1) 2 or more DIFFERENT elements
• 2) Held together by CHEMICAL BONDS
• 3) The type of ATOM the BOND determine the
  properties (small note sheet)

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Compounds..

• Important characteristics of COMPOUNDS
• have a definite composition
• can be broken down into simpler substances by
  chemical means
• can be identified by their physical properties
• Compounds usually have very different properties
  than the elements that compose them
• EX Ca (soft, silvery metallic solid needed by
  humans) Cl (greenish-yellow gas poisonous to
  humans) BUT..CaCl (nonpoisonous white solid used
  to melt ice on streets) ?

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Molecules (small note sheet)

• Def A group of atoms held together by a
  covalent bond. EX Water
• Molecules Compounds
• Atoms Elements
• (note sheet)
• Chemical formulas use chemical symbols and
  subscripts to show how many atoms of those
  elements are combined in the compound (RATIO!)

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Chemical Formulas (small note sheet)

• Formulas are written with chemical symbols and
  subscripts which indicate the of times that
  element appears in the molecule.
• Elements without a subscript have an imaginary
  1
• H2O subscript indicates 2 hydrogen atoms and 1
  oxygen atom (water)
• CO2 1 carbon with 2 Oxygen (carbon dioxide)
• C3H8 3 carbon with 8 hydrogen(propane)
• C6H12O6 6 carbon, 12 hydrogen, and 6 oxygen
  (glucose)

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Fill in the Chart (pls place in ntbk) (please
just do a practice one in notebook w/notes)
Compound Symbol and of atoms Total of atoms
Na2SO4 Na2,S1,O4 7
Al2O3
CaSO4
C2H6
Fe
NH3
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(small note sheet)

• The SAME elements can be used to form VERY
  DIFFERENT compounds with DIFFERENT properties.

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(small note sheetWATER vs HYDROGEN
PEROXIDE

• H2O2
• 22
• Clear
• Colorless
• Odorless
• Thick, Syrupy
• Kills Bacteria
• Poisonous if ingested
• Can be used as fuel

• H2O
• 21
• Clear
• Colorless
• Odorless
• Needed for Survival

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• NITROGEN OXYGEN
• Nitrogen Monoxide By product of combustion of
  substances in air, engine, fossil fuels, power
  plants, lightning
• Nitrous Dioxide Brown toxic gas, major air
  pollutant, used in racing
• Nitrous Oxide Used by dentist, surgery as mild
  anesthetic, greenhouse gas
• (just COOL INFO!!)

• NO ( 1N , 1O)
• NO2 ( 1N , 2O)
• N2O ( 2N, 1O)

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N2O Nitrous Oxide
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2.2D Chemical Bonds (small note sheet)

• Chemical bonds are forces (the glue) that hold
  atoms together. 2 types
• Ionic Bonds valence electrons completely
  transferred
• Covalent bonds valence electrons shared

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IONIC BONDS

• Attraction between () (-) ions ionic
  bonds
• Ionic compounds are very stable their
  strong crystal
• structure , shatters,
  separates into ions when
• dissolved conduct electricity, high
  Boiling Point
• Melting point
• Naming ionic compounds Positive Ion always
  named 1st
• Negative Ion is named by dropping last part
  of name adding the suffix
  ide
• EX Sodium Chloride (NaCl-)

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PROPERTIES OF IONIC BONDS (small note sheet)

• IONIC BONDS.
• occur when metals react with nonmetals
• hard (think of a LEGO structure)
• brittle
• high melting boiling points
• transfer of electrons
• conduct electricity when dissolved in water
• EX salt, concrete, sulfuric acid

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COVALENT BONDS

• Electrons are SHAREDneither atom loses or
  gainsSONO IONS are formed!
• SHARED ELECTRONS are attracted to both positively
  charged nuclei
• EX H2, N2, O2..
• The of covalent bonds an atom can form depends
  on the of electrons available for sharing
• POLAR COVALENT when electrons are shared
  unequally (polar-anything that has 2 extremes)
• EX H2O

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PROPERTIES OF COVALENT BONDS

• COVALENT BONDS
• electrons shared between nonmetal and nonmetal
• not hard (think of a plastic ball pit)softer
• not brittle
• low melting boiling points
• dont conduct electricity well usually dont
  dissolve in water are usually more flammable
• EX O2, CO2, methane, hydrochloric acid, candy
  corn

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Atomic Theory

• Proposed in 1808 by John Dalton.
• All matter is composed of atoms
• Atoms of a given element are identical
• Atoms of different elements combine in simple,
  whole- number ratios to form chemical compounds

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3.3D-Chemical Reactions Involve ENERGY Changes

• Bond energy energy associated with bonds
  between atoms
• Breaking bonds uses (requires) energy
• Forming bonds gives off (releases) energy

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IF

• More energy is RELEASED than added
• EXOTHERMIC REACTION
• Reactants YIELD PRODUCTS ENERGY
• (baggy of Yeast Hydrogen Peroxide)
• More energy is ABSORBED than released
• ENDOTHERMIC REACTION
• Reactants Energy YIELD PRODUCTS
• (baggy of Baking Soda Vinegar)

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Exothermic Endothermic Reactionswork together
to CREATE SYSTEMS OR CYCLES!!

• PHOTOSYNTHESIS making glucose (sugar) Oxygen
  from Carbon Dioxide,Water Energy
• ENDOTHERMIC
• 6CO2 6H2O Energy C6H12O6 6O2
• CELLULAR RESPIRATION reverse of photosynthesis,
  the production of Carbon Dioxide, Water Energy
  from combustion of glucose, using Oxygen
• EXOTHERMIC
• C6H12O6 6O2 6CO2
  6H2O Energy

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Exothermic Endothermic Reactionswork together
to CREATE SYSTEMS OR CYCLES!!

• PHOTOSYNTHESIS making glucose (sugar) Oxygen
  from Carbon Dioxide,Water Energy
• ENDOTHERMIC
• 6CO2 6H2O Energy C6H12O6 6O2
• CELLULAR RESPIRATION reverse of photosynthesis,
  the production of Carbon Dioxide, Water Energy
  from combustion of glucose, using Oxygen
• EXOTHERMIC
• C6H12O6 6O2 6CO2
  6H2O Energy

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REVIEW ?

• CHEMICAL REACTION HINTS.
• 1) Temperature Change
• HeatEnergyProduced
• ?

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• FIRE
• COMBUSTION
• EXPLOSION

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• Your shirt has white spots because you dyed eggs
  using vinegar?

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• COLOR CHANGE

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• BUBBLES ARE PRESENT???

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• GAS PRODUCED

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• A SOLID IS FORMED.when u started with LIQUIDS????

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• PRECIPITATE