Download The Chemical Basis of Life Chapter 4

The Chemical Basis of Life
Chapter 4
Required Elements
Structure of Atoms
Chemical Bonds
Properties of Water
4.1 - Life Requires About 25
Chemical Elements
• Matter
– Elements
• 25 Essential
• Trace Elements
– Compounds
What is Matter?
Matter
Not Matter
How is Matter Organized?
•Divided into pure substances or
mixtures based on composition.
–Pure substance
•Uniform composition with same
properties throughout
•Can be classified as either an element
or a compound
Element
•Cannot be broken
down into simpler
substances
•Made of only one type
of atom
•Represented by 1-2
letters
25 Essential Elements
•
•
25 of 92 natural elements are essential
to life
CHNO – 96% of living organisms
Trace Elements
• Elements that make up less than 0.01
percent of you body mass, but are critical
to your health.
Compound
•Made from two or more simpler
substances
•Can be broken down into those
simpler parts
•Always contains 2 or more elements
4.2 – Chemical Properties are
Based on the Structure of Atoms
• Atoms
• Subatomic Particles
– Electrons
• Reactivity
– Nucleus
• Protons
– Atomic Number
• Neutrons
– Isotopes
– Radioactive Isotopes
• Electrons and Reactivity
The Atom
• The atom is the smallest part of an
element that retains all the characteristics
of that element.
• A Greek scientist named Democritus was
one of the first to propose that all matter
was composed of tiny particles called
atoms
Sub Atomic Particles
• Electrons orbit the
nucleus (a little)
like planets round
the sun. Electrons
reside in specific
shells or orbitals.
• The three parts of
the atom are called
sub atomic
particles.
Sub Atomic Particles
• The nucleus of an atom
contains protons and
neutrons.
• They are held together
by a strong force which
keeps the positively
charged protons from
repelling one another.