02. Basic chemistry.Ian Anderson (2013)Saint Ignatius College Geelong
Knowledge and skills. Distinguish between an atom, an element, a molecule,    an ion and a compound.   List the importan...
Atoms.          Atoms are the building           blocks of all matter.          An atom has             A central nucle...
Ions.                        If an atom gains or loses an                         electron it becomes a charged          ...
Elements.                               Substances that consist of only                                one type of atom. ...
Molecules and compounds.               Molecules = Two or more atoms                held together by chemical            ...
Chemical bonding. The atoms that make up a molecule are held together by either   Covalent bonds   Ionic bonds, or   M...
Covalent bonding.                     Only occurs between two                     non-metals.                       e.g....
Ionic bonding.                       Only occurs between a metal                        and a non-metal.                 ...
Polar molecules.               Sometimes in a covalent bond oneWater (H2O)                atom attracts the shared electr...
Hydrogen bonding.                                        Resulting from the attraction ofWater (H2O)        δ-           ...
Basic chemistry
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Basic chemistry

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Basic chemistry

  1. 1. 02. Basic chemistry.Ian Anderson (2013)Saint Ignatius College Geelong
  2. 2. Knowledge and skills. Distinguish between an atom, an element, a molecule, an ion and a compound. List the important elements found in living organisms. Describe the difference between covalent and ionic bonding. Explain what polar molecules are. Describe how hydrogen bonds may form within or between molecules with polar covalent bonds.
  3. 3. Atoms.  Atoms are the building blocks of all matter.  An atom has  A central nucleus composed of  Positively charged protons.  Uncharged (neutral) neutrons.  Negatively charged electrons orbitting around the nucleus.  The overall charge of an atom is neutral.
  4. 4. Ions.  If an atom gains or loses an electron it becomes a charged ion.  Loses one or more electrons  positive ion (cation).  Gains one or more electron Na  Na+ + e-  negative ion (anion). H  H + + e-  The charge of an ion means that it will be attracted to or O+ 2e-  O2- will repel other ions (important in ionic bonding).
  5. 5. Elements.  Substances that consist of only one type of atom.  Of the 92 naturally occurring elements  Only 11 are found in organisms in more than trace amounts.  Four of these 11, Carbon (C), hydrogen (H), oxygen (O) and nitrogen (N) make up 99% of Carbon Oxygen organisms by weight.•6 protons •8 protons  What makes one element•6 neutrons •8 neutrons different to another is the•6 electrons •8 electrons number of protons its atoms has.
  6. 6. Molecules and compounds.  Molecules = Two or more atoms held together by chemical bonds.  e.g. H2, O2, CO2, CH4 O=O  Compound = a molecule O2 containing two or more different types of atoms.  e.g. CO2, CH4, H2O Note: All compounds are molecules. Not all molecules are compounds!
  7. 7. Chemical bonding. The atoms that make up a molecule are held together by either  Covalent bonds  Ionic bonds, or  Metallic bonding (not relevant here). Atoms combine with other atoms in order to become more stable.  Atoms are most stable when they have a full outer shell [like the noble gases in Gp18].
  8. 8. Covalent bonding.  Only occurs between two non-metals.  e.g. O2, CO2, H2O, C6H12O6  Involves the sharing of electrons. Methane (CH4)  Covalent bonds are stronger than ionic bonds (generally).
  9. 9. Ionic bonding.  Only occurs between a metal and a non-metal.  e.g. NaCl, CaCl2  Involves one atom donating an electron (or electrons) to the other. The two (now) ions are held together by the Sodium chloride electrostatic forces of attraction (NaCl) (one ion has a +ve charge and the other has a –ve charge).  Ionic bonds are easier to break than covalent bonds (generally), but are still strong.
  10. 10. Polar molecules.  Sometimes in a covalent bond oneWater (H2O) atom attracts the shared electron more strongly than the other atom resulting in unequal sharing of electrons.  Even though the overall charge of the molecule is still neutral, there is a slightly positive region and a slightly negative region.  The polarity of molecules is an important property.  e.g. Polarity governs the way that many molecules cross cell membranes.  e.g. H2O, sugars and amino acids.
  11. 11. Hydrogen bonding.  Resulting from the attraction ofWater (H2O) δ- the slightly positive hydrogen atom on one polar molecule and the slightly negative atom δ- (usually oxygen or nitrogen) in δ+ δ+ another polar molecule.  Only occurs between polar δ+ δ+ molecules.  Much weaker than both covalent and ionic bonds.  Play an important role wrt the properties of water and the structures of both DNA and proteins.

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