The Chemistry of Life

1
The Chemistry of Life

• Biology Chapter Two

2
Atoms

• An atom is the smallest unit of matter that
  cannot be broken down by chemical means
• Consists of 3 particles
• electrons (- charge)
• Protons ( charge)
• Neutrons (no charge)

3
Elements

• Elements are pure substances made of only one
  kind of atom there are over 100 known elements
• Elements differ in the number of PROTONS their
  atoms contain

4
Isotopes

• Atoms of an element that contain different
  numbers of neutrons are called isotopes.
• EX isotopes of Carbon carbon-12, carbon-13,
• carbon-14
• Each contain 6 protons but different neutrons

5
Periodic table, pages 1046, 1047
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Compounds

• A compound is a substance made of the joined
  atoms of two or more different elements.
• Ex NaCl, sodium chloride
• H2O, water
• NH3, ammonia

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Covalent Bonds

• Covalent bonds form when two or more atoms share
  electrons to form a molecule
• Example H2O, water

8
Hydrogen Bonds

• A hydrogen bond is a weak chemical attraction
  between polar molecules
• Polar molecule a molecule that has opposite
  charges (polarity) (/-)

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Hydrogen Bonding in Water Molecules
10
Ions and Ionic Bonds

• An atom that has gained or lost electrons is
  called an ion.
• Ions of opposite charge (/-) may interact to
  form a ionic bond.
• Ex NaCl (sodium chloride)

11
Water and Solutions

• Fun Facts
• Water makes up 70 of your body!
• 2/3 of the molecules in your body are H2O
  molecules
• Most cellular events take place in H2O
• Water absorbs heat more slowly and retains this
  energy longer! (compared to other liquids)

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• Cohesion attraction between substances of the
  SAME kind

13

• Adhesion attraction between DIFFERENT
  substances

14
Acids and Bases

• While the bonds in water molecules are strong, at
  any given time a tiny fraction of those bonds
  might break, forming a hydrogen ion, H, and a
  hydroxide ion, OH-
• H2O ? H OH-

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• Acid form hydrogen ions when dissolved in water
• Base form hydroxide ions
• Acidic Neutral Basic