Transcript Chapter 2 Chemistry of Life….

Chapter 3.1
Chemistry of Life….
 Atom – basic unit of matter
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It is the simplest unit of matter with its own physical and
chemical properties
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Made up of sub atomic particles
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Neutrons (+/-)
Protons (+)
Electrons (-)
 The number of electrons and protons are the same
giving the atom a neutral charge
Atom’s Structure
 1. Nucleus
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Contains Protons and Neutrons
Has a positive charge
 Protons and Neutrons have the same mass
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 2. Electron Cloud
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Electrons are located here
They are in constant motion
Very small
Electrons
 Very energetic
 Very small
 Move at high speeds
around the nucleus in
random directions
 Different energy levels
in the electron cloud
Electrons (continued)
 Energy levels
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The levels farther from
the nucleus have more
energy
To make most atoms
stable their outer
energy level must be
filled with eight
electrons
Electrons can gain/lose
energy by switching
levels
Elements
 Composed of entirely the same type of atoms
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More than 100 elements
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90 % of living things are composed of Oxygen,
Carbon, Hydrogen, and Nitrogen
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Each element has a symbol
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Arranged in the periodic table
Elements continued…
 The amount of protons in an atom is its
atomic number
Compounds
 Most elements do not naturally exist by
themselves
 Compounds
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Pure substances that are made up of atoms of
two or more elements
 Chemical Equations show the ratios
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H2O & C2H3O2
Compounds (continued)
 When elements
combine their physical
properties change
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Sodium + Chlorine
Sodium in natural form is
highly volatile
 Chlorine is poisonous
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Together they form table
salt
Compounds (continued)
 Most elements combine to fill outer energy
levels with eight electrons
 Elements with less than eight atoms in their
energy levels tend to undergo chemical
reactions
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Form new bonds with other atoms
Covalent Bonds
 Def. – a bond that forms when two atoms
share one or more pairs of electrons
 SHARING OF ELECTRONS
 Molecules
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A chemical structure composed of one or more
atoms
Water – it is always one 2 hydrogen atoms and 1
oxygen atoms
Ionic Bonds
 An ionic bond is
formed when one
atom gives up an
electron to another.
The positive ion is
then attracted to a
negative ion to form
the ionic bond