“Bohr”ing you with atoms

The study of
chemistry begins with
the basic unit of
matter, the atom.
 What is matter?
 Anything that has
mass and takes up
space.
The subatomic particles that make
up atoms are
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Protons (+) are positive
located in the center of
atom
Neutrons (=) neutral
located in the center of
the atom
Electrons (-) negative
and are located in space
around the nucleus. They
are 1/1840 the size of a
proton.

Because protons and
electrons have equal and
opposite charges, atoms
are neutral.
Elements and Isotopes

Element is one type
of atom.
 Their are over 100
elements in
existence, but only a
few are fond in living
organisms.
 Atom Builder
6
C
12.011
Carbon
Isotopes

Are atoms of the
same element with a
different number of
neutrons.

All 3 isotopes have
the same chemical
properties, because
they all have the
same number of
electrons.
Nonradioactive carbon-12 Nonradioactive carbon-13
6 electrons
6 protons
6 neutrons
6 electrons
6 protons
7 neutrons
Radioactive carbon-14
6 electrons
6 protons
8 neutrons
How radioactive isotopes work

When an organism is
alive it constantly
absorbing (C-14).
 However when an
organism dies the C14 begins to break
down, ½ the quantity
of death every 5,730
years.
 Web site (ingest)
Radio Active Isotopes

Have unstable nuclei
and break down at a
constant rate over
time.
 Geologist use
radioactive isotopes
to determine the age
of a fossil. (C-14)
Other Radioactive Isotopes

Can be used
 To treat cancer
 Kill bacteria
 As “tracers”
Chemical Compounds

Are formed when
molecules of two or
more atoms are
joined together.
 The chemical
properties of a
compound are very
different from the
elements it is made
up of.
Two Types of Compounds

Inorganic compounds
 Lack Carbon
 Non living
 For example water is
made up of 2
hydrogen’s and 1
oxygen.

Organic compounds
 Contain Carbon
 Must come from other
living things.
Sodium and Chloride

Are very different
elements.
 Chlorine (Cl) is a
poisonous green gas
that was used to kill
soldiers in WWI.
 Sodium (Na) – is a
silvery metal.
Chemical Bonds

Atoms in compounds
are held together by
chemical bonds.
 Bond formation
involves the electrons
that surround each
nucleus known as
valance electrons.
Ionic Bonds





An Ionic bond is formed
when one or more
electrons are
transferred from one
atom to the other.
An atom that loses an
electron has a (+) charge.
An atom that gains an
electron has a (-) charge.
Positively or negatively
charged atoms are known
as ions.
Ionic bonds are not very
strong.
Ionic Bonds: One big greedy thief
 Ionic bonding can be best dog
imagined as one big



greedy dog steeling the
other dog’s bone.
The bones represent the
electrons up for grabs.
When the big dog gains
an electron he becomes
negative, and when the
little dog looses an
electron he becomes
positive.
The two ions are
attracted very strongly to
each other as a result of
the opposite charges.
Covalent Bonds

Covalent bond is
formed when
electrons are shared
between atoms.
 Very strong bond.
Covalent Bond: Dogs of equal
strength

Covalent bonds can
be thought as two or
more dogs with equal
attraction to the
bones. Since the
dogs (atoms) are
identical, then the
dogs share the pairs
of available bones
evenly.
Molecules

When atoms are
joined together by a
covalent bond, they
form molecules.
 The molecule is the
smallest unit of most
compounds.
Van der Waals forces



Some atoms have a
stronger attraction fore
electrons than do other
atoms. There for, when
atoms in a covalent bond
share electrons their not
always equal.
A slight attraction can
develop between the
oppositely charged
regions of nearby
molecules.
The results are ever
changing “hot spots” of
positive and negative
charge that enable all
atoms to stick together.
Van der Waals forces in Action




A geckos foot is covered by as
many as a ½ a million tiny hair
like projections.
Each projection is divided into
hundreds of tiny flat –surfaced
fibers.
This design allows the gecko’s
foot to come in contact with an
extremely large area of the wall
at the molecular level allowing
Van’s forces to occur.
The combined strength of all
the Van der Waals froces allows
the gecko to walk up walls.
Polar Covalent Bonds

A type of covalent
bond that differs in
electronegativity.
 The electrons are
pulled closer to the
larger atom, making it
slightly negative and
the other slightly
positive
 An example of a polar
molecule is water.
Hydrogen Bonding

Water is a polar
molecule.
 Water has a partial
positive an negative
charge. The (O) is (-)
and the hydrogen’s
are (+).
 Hydrogen bonds are
weak.
 Shock wave demo
Match the Bonds
Water has strong cohesion and
high surface tension



Cohesion- is the
attraction between
molecules of the same
substance.
A single water molecule
may be involved in as
many as 4 hydrogen
bonds at the same time.
Cohesion explains why
some insects can walk on
water.
Water adheres to other molecules


Adhesion is an attraction
between molecules of
different substances.
The surface water in a
graduate cylinder dips
slightly in the center
because the adhesion
between water molecules
and glass is stronger than
the cohesion between
water molecule.
Ice Floats

Unlike most
substances when
water freezes it
expands, and
becomes less dense.
 What effects would
that have on life?
Water is an excellent solvent




Water is a solvent – the
substance in which the
solute is dissolved.
In a salt-water solution,
table salt is the solute.
Water is the solvent of
life.
Dissolve demo
Water has a high heat capacity

Water changes
temperature very
slowly.
 Thus the temperature
of large bodies of
water are very stable.
Evaporative Cooling

As water evaporates,
the surface of the
water that remains
behind cools down.
 Why do we sweat
more on a humid
day?
Mr. Walcott
before a job
interview
What gives water its special
properties



Individual water
molecules are polar and
they stick together by
means of hydrogen
bonds.
Hydrogen bonds are
weak and only last a
fraction of a second.
It takes a lot of energy to
overcome the combined
attraction of many
hydrogen bonds.



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This explains
Waters great capacity to
store heat
High boiling point
Surface tension
Acid, Bases, and pH
Water

Hydrogen Ion (H+)

Hydroxide Ion (OH-)
Acids (H+)
 An


acids from H+ ions in solutions
have more H+ ions than pure water
pH values below 7
Bases (OH-)
 Produce
hydroxide ions (OH-)
 Have lower amounts of H+ ions then pure
water.
 pH values above 7
Buffers

Weak acids or bases
that can react with
strong acids or bases
to prevent sudden
changes in pH.
 The human body has
a buffer system.
 The most common
buffer is the
bicarbonate ion.
The pH scale





The pH scale tells us how
many H+ ions there are in
a solution.
The higher the pH the
more basic the solution
The lower the pH the
more acidic a solution is.
pH of 7 is neutral
pH scale animation
What to do when you get stung

When a wasp stings it
injects an alkali
(base) into the victim
 You can neutralize
the sting with vinegar
(an acid)
Tums

Are a base
 Neutralize the
stomachs acids.