Essential Chemistry for Biology
CHAPTER 2
• Elements and the Periodic Table
• Atoms and Subatomic Particles
• Atomic Number, Mass, and Isotopes of Elements
• Chemical Bonding and Molecules
• Chemical Reactions
• Properties of Water
• pH and Acid/Base Balance
C - Carbon
Periodic Table of the Elements
He - Helium
Fe - Iron
(from ferrum)
Al Aluminum
Au - Gold
(from aurum)
Cu - copper
(from cuprum)
Elements are fundamental categories of
matter that cannot be broken down into
other types of matter.
The Elements Found in Living Things
Life is made mostly of “CHON”
Figure 2.3
Essential Chemistry for Biology
CHAPTER 2
• Elements and the Periodic Table
• Atoms and Subatomic Particles
• Atomic Number, Mass, and Isotopes of Elements
• Chemical Bonding and Molecules
• Chemical Reactions
• Properties of Water
• pH and Acid/Base Balance
Every Element (Category) is Composed of Atoms
The element gold (Au)
Atoms Are the Apples in the Bins Called Elements
• Atoms (apples) are the individual items belonging to a specific element
(variety) in the Periodic Table.
• Atoms belonging to an element are very similar but not identical (they
have slightly different masses)
Three atoms (apples)
from the variety
(element) Golden
Delicious
24.2 g
Periodic Table of Apple Varieties
29.6 g
25.9 g
Atoms Are Composed of Three Types of Particles
Atoms of an Element Always Have a Unique Number of Protons
Boron Carbon Nitrogen Oxygen Fluorine
Neon
The number of electrons = number of protons in an electrically balanced atom
Different Orbits or Shells Have Different Capacities For Electrons
Figure 2.7
Essential Chemistry for Biology
CHAPTER 2
• Elements and the Periodic Table
• Atoms and Subatomic Particles
• Atomic Number, Mass, and Isotopes of Elements
• Chemical Bonding and Molecules
• Chemical Reactions
• Properties of Water
• pH and Acid/Base Balance
A Closer Look at the Numbers For Each Element
Numbers That Define Elemental Size and Behavior
Elements are organized by:
• Size and numbers of parts
• Chemical behavior
12.011
Heavier elements
are to the right
and downwards
in rows
Elements with
similar behavior
are in the same
column
Electron Arrangement and the Chemical Properties of Atoms
Atoms of elements with the same
number of outer shell electrons
have similar chemical behavior.
Both nitrogen at bismuth form 3 bonds with neighboring atoms
Isotopes are alternate atomic forms for an element.
Three “isotopes” of Golden Delicious
24.2 g
29.6 g
25.9 g
Mass number is the average mass of the different isotopes found in nature.
Radioactive Isotopes can be used to form images
Positron Emission Tomography (PET) scan looks for where radioactive
fluorine-sugar is being used in the brain (blue areas)
Essential Chemistry for Biology
CHAPTER 2
• Elements and the Periodic Table
• Atoms and Subatomic Particles
• Atomic Number, Mass, and Isotopes of Elements
• Chemical Bonding and Molecules
• Chemical Reactions
• Properties of Water
• pH and Acid/Base Balance
Chemical Bonding and Molecules
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decompressor
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QuickTime™ and a
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NaCl
(sodium chloride)
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H 2O
Three types of chemical bonds
• Ionic bonds
• Covalent bonds
• Hydrogen bonds
Ionic Bonds Are Formed Between Two or More Electrically
Unbalanced Atoms (Ions)
Covalent Bonds Are Sharing Arrangements
Between Two Atoms
When A Molecule Becomes Polar
Hydrogen Bonds: Bonds Between Polar Molecules
Essential Chemistry for Biology
CHAPTER 2
• Elements and the Periodic Table
• Atoms and Subatomic Particles
• Atomic Number, Mass, and Isotopes of Elements
• Chemical Bonding and Molecules
• Chemical Reactions
• Properties of Water
• pH and Acid/Base Balance
Chemical Reactions
Essential Chemistry for Biology
CHAPTER 2
• Elements and the Periodic Table
• Atoms and Subatomic Particles
• Atomic Number, Mass, and Isotopes of Elements
• Chemical Bonding and Molecules
• Chemical Reactions
• Properties of Water
• pH and Acid/Base Balance
Water’s Life-Supporting Properties
• Cohesion
• Adhesion
• Capillary action
• Surface tension
• Moderates temperature change
• Less dense as a solid
• Universal solvent
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decompressor
are needed to see this picture.
Water Can Dissolve A Large Number Of Substances
Table salt
(NaCl) in water
• Water surrounds ions and polar molecules, pulling them apart from each
other and dissolving them. Substances that dissolve in water are called
hydrophilic.
• Water cannot dissolve non-polar (hydrophobic) molecules like oil, fat,
and grease.
• Since the majority of substances on earth are hydrophilic, water is called
the universal solvent.
Figure 2.16
Essential Chemistry for Biology
CHAPTER 2
• Elements and the Periodic Table
• Atoms and Subatomic Particles
• Atomic Number, Mass, and Isotopes of Elements
• Chemical Bonding and Molecules
• Chemical Reactions
• Properties of Water
• pH and Acid/Base Balance
Water Breaks Can Break Apart to Form Ions
H2O
water
H+
hydrogen ion
+
OHhydroxide ion
• When liquid water is pure, it has an equal number
of hydrogen and hydroxide ions (H+ = OH-). Pure
water is neutral.
• Some substances, when added to water give off H+ and
create acidic conditions (H+ > OH-). These substances are
acids.
• Other substances when added to water give off OHand create alkaline or basic conditions (H+ < OH-).
These substances are called bases or alkali.
• Organisms cannot survive in acidic or basic
conditions because their chemicals are broken apart
The pH Scale Is Used to Measure Acidity or Basicity
Buffers
• Substances called
buffers can inhibit pH
change when part of a
water solution
• Buffers soak up added
H+ or OH- like chemical
sponges
• Humans have
bicarbonate buffer in
their blood to prevent
pH change when eating
and drinking.
Essential Chemistry for Biology
CHAPTER 2
• Elements and the Periodic Table
• Atoms and Subatomic Particles
• Atomic Number, Mass, and Isotopes of Elements
• Chemical Bonding and Molecules
• Chemical Reactions
• Properties of Water
• pH and Acid/Base Balance