2.1 / 2.2 Study Guide
2.1—Atoms, Ions, and Molecules
 The atom is the smallest basic unit of matter
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It has 3 parts
o Protons—in nucleus (positive charge):
element’s identity
o
Neutrons—in nucleus (neutral charge):
o
Electrons—around nucleus (negative charge):
Atoms can lose, gain, or share electrons to become
more stable
o Transfer of e- ionic bond
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Metal and nonmetal: example: Sodium Chloride NaCl
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o
Lose e-? Become more positive
Gain e-? Become more negative
Sharing of e- Covalent bond
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Example: water H2O
When 2 or more atoms are covalently bonded, it is called a molecule
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Ion is an atom that has lost or gained electrons. Na+ or Cl-
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An element is one particular type of atom that cannot be broken down into a simpler substance by
ordinary chemical means. Example: Na, C, H, O or Cl
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A compound is a substance made up of two or more elements in a definite ratio. Example: NaCl, H2O,
CH4
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Most important elements for living things Carbon, Hydrogen, Oxygen, Phosphorus, Sulfur, Nitrogen_
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Why is carbon unique – valence number of 4 so it can form many bonds
2.2—Properties of Water
 There are three important properties of water
o High specific heat: water resists changes in
temperature
o
o
Cohesion: attraction among molecules of
the same substance
 Makes water stick togethersurface
tension
Adhesion: Attraction among molecules of
different substances
 Meniscus
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Water is a polar molecule
o Uneven sharing of e Oxygen side more negative; Hydrogen side more positive
o
Slight attraction between different water molecules
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Bonds formed between polar compoundsHydrogen bonds
 Important for protein/nucleic acid structure
Water is the universal solvent
o
Many things dissolve in water
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o
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Mixture of a substance that is the same throughout solution
Substance that dissolves another substance solvent
Substance that is dissolved by a solvent solute
Acids: Compounds that release H+ when dissolved in water
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pH less than 7
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examples of acids vinegar, lemon juice, tomatoes, coffee
Bases: Compounds that release OH- when dissolved in water
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pH greater than 7
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examples of bases ammonia, bleach, detergents, seawater
o
Neutral: pH of 7 water
o
Buffer: Chemicals that regulate the pH of the body, preventing sharp changes in pH