NOTES: 2.1

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NOTES 2.1 The Nature of Matter
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Key Questions

• Identify the three subatomic particles found in
  atoms.
• Explain how all of the isotopes of an element are
  similar and how they are different.
• Explain how compounds are different from their
  component elements.
• Describe the two main types of chemical bonds

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What makes up all matter?

• A chemical element is a pure substance that
  consists of just one type of atom.
• Atoms are the basic unit of matter.
• The atom is the smallest unit which retains all
  of the physical and chemical properties of its
  element.

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• Chemical Compound - A substance formed by the
  chemical combination of two or more elements in a
  fixed proportion.
• The properties of the compound are usually very
  different from the elements that make up the
  compound.

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Examples of Compounds

• Water - H2O
• Salt NaCl
• Methane CH4
• Titanium Dioxide TiO2

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Examples of Compounds
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Properties of Elements
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Three Subatomic Particles
Particle Charge Location Mass
Proton () Nucleus 1.0007 amu
Neutron Neutral Nucleus 1.0008 amu
Electron (-) Orbiting nucleus 0.0005 amu
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• Atomic Number
• -the number of protons in an atom of an element
• all atoms of an element have the same atomic
• written as a subscript next to the elements
  symbol
• in a neutral atom, the number of protons is equal
  to the number of electrons (balanced charges).

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• Mass Number
• -the number of protons and neutrons in an
  atom of
• an element.
• The number of neutrons may vary, but the proton
  number remains constant.
• Written as a subscript next to the elements
  symbol

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Isotopes-

• -Atoms of an element that have more or fewer
  neutrons.

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Isotopes-

• in nature, elements occur as mixtures of
  isotopes.
• some are radioactive unstable isotope where
  nucleus decays emitting sub-atomic particles
  and/or energy

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Half-Life

• the time it takes for half the nuclei in a
  radioactive isotope sample to decay

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Energy Level of Electrons
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Chemical Bonding
Covalent Bond strong chemical bond between
atoms formed by electrons being shared by the
atoms.
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• Ionic Bond
• bond formed by the attraction of a positive ion
  to a negative ion
• Anion positive ion
• Cation negative ion

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Chemical Reactions bonds between atoms are
formed or broken, causing substances to combine
and recombine as different molecules
CH4 O2 CO2 H2O
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Chemical Reactions

• All of the chemical reactions that occur within
  an organism are referred to as that organisms
  metabolism

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Chemical Reactions

• Reactants
• the substance(s) at the beginning of a reaction
  shown on the left side of the equation
• Products
• the substance(s) at the end of a reaction shown
  on the right side of the equation.

CH4 O2 CO2 H2O