•What’s Important About
the Nutrition Label?
• What
• Why
does the label tell you?
is this important?
•Unit 3:The Chemistry of Life
• Unit Objective:
• To
identify the carbon-based organic
molecules of life and understand the roles
they play in life processes.
• Lesson Objective:
• To know how an atom is constructed and
how each element’s properties determines
how the formation of compounds (bonding)
takes place.
Only copy down underlined material.
Everything else is there for support.
•First Question…
• Why
do we study CHEMISTRY in BIOLOGY class…
• https://youtu.be/fgQLyqWaCbA
• So.
Why do we?...
•What Are Organisms Made Of?
•
Every organism is different depending upon it’s role or
needs but there are basic elements that are universal to
life on Earth.
•The Basic Compounds of Life.
•
Regardless of the amount, most organisms use elements
to form these Macromolecules of Life.
1.
2.
3.
4.
•
These are the fundamental molecules of life that you will
be required to know.
•
•
Fats
Proteins
Sugars
Nucleic Acids.
These carbon-based molecules are known as Organic Compounds.
Another molecule you will learn about in this mini-unit
is water.
•Essential Questions
•
•
How does hydrogen, carbon, and oxygen combine to form
molecules that participate in living systems?
What do these molecules do to support life?
•Objectives
•
•
•
•
•
To review/identify what makes up matter.
To know the elements that form most organic molecules.
To review/understand why atoms form bonds.
To understand how and why these bonds are essential for
life by forming the carbon-based organic molecules of life.
This information will help you soon be able to explain how
these molecules participate in important processes in living
things.
•1st Step
• Get
into groups.
• Use your resources to fill in the blanks and
answer the questions.
• Tomorrow we’ll discuss and get any
questions answered.
•Vocabulary
• Atoms
• Element
• Valence
electrons
• Compound
• Molecule
• Ion
•Before You Learn About the Organic Macromolecules…
• You
must understand that all bigger molecules
are built of smaller pieces.
Everything of atoms…
• Sometimes arranged into basic molecules.
•
• These
smaller pieces are called…
• These
will sometimes be called… (a.k.a.)
• What
•
is a subunit?
Something that is combined with other subunits to
build something bigger.
•Atoms
Every living and nonliving thing is made of matter.
• Matter is anything that has mass and takes up space.
•
All matter is made of very
small particles called atoms.
• An atom is the smallest unit
of matter that cannot be
broken down by chemical
means.
•
•Atoms
• The
atom is composed of three main types of
smaller “subatomic” particles.
• Protons:
positively
charged particles.
• Neutrons: particles
with no charge.
• Electrons:
negatively charged
particles.
•Atoms
• The
particles are in two specific areas:
The nucleus.
• The electron cloud.
•
• Protons
and neutrons are in the nucleus.
• Electrons are in various energy levels
contained in the electron cloud around the
nucleus.
What are the parts of an atom?
B
C
A
D
•How Is an Atom Built?
Find carbon on the periodic table.
• This is the information for the element CARBON
• Notice its row and column.
•
• Every
box represents a different element.
An element is any quantity of a substance that is
100% the same type of atom.
• Being the same type means they have the same # of
protons.
•
•
Ex: Diamonds are always the element carbon, regardless of the
size, because every atom has 6 protons.
•CHNOPS: What are the Most Abundant
Elements in Biology?
•
•
The six highlighted below are the most abundant elements in the
bodies of most biological organisms.
Take out the periodic tables & Mark these in your Periodic Table.
•Reading the Periodic Table
• Atomic
Number
• Symbol
• Name
• Atomic
Mass
•Atomic Numbers, Mass, Electrons…
• The
boxes give a lot of information.
• How do you know how many protons,
electrons, and neutrons an element has?
• It’s all based upon the atomic number found
in the periodic table.
• Atomic
#
• # electrons
• # neutrons
= # protons
= # protons
= atomic mass - # protons.
•What Happens When an Atom Gains or
loses an Electron is Ionic.
Usually, atoms by themselves if stable will have equal
numbers of protons & electrons.
• If this is the case the charges cancel and they are neutral.
• If an atom gains or loses electrons they become ions.
• Ions are atoms that have a charge because the protonelectron numbers don’t match.
• Ions are formed by electrons ‘jumping’ from one atom to
another.
•
•Formation of Ions: Count the p+ & ebefore & after the exchange…
Anion:
A negatively
charged ion.
Cation:
A positively
charged ion.
+
Na
Cl
Sodium
Before
After
Chlorine
Before
After
Protons
+11
+11
Protons
+17
+17
Electrons -11
-10
Electrons -17
-18
Total
+1
Total
-1
0
0
•Special Circumstance: Isotopes
Elements
• Recall, elements are all the same type of atom because
every atom has the same number of protons.
•
•
•
For example, every atom for any amount of the element
carbon has six protons.
There are several types of carbon though.
Atoms of an element can have different numbers of
neutrons.
• Isotopes
are atoms of elements that have a
different number of neutrons.
•
Isotopes create challenges and benefits because bonds form
differently and are usually radioactive to a degree.
•Isotopes
• Because
Isotope atoms have
the same number of
protons, and also electrons,
isotopes have the same
chemical properties.
• However, isotopes are
unstable and release
radiation as they decay
(shed the extra neutrons)
•
Some radiation is worse than
others.
•The Numbers Really Matter
• The
numbers represent an atom’s proton,
neutron, and electron number when it is unbounded and electrically neutral.
• Atoms are rarely like this, stable, in nature.
• Mainly because the electrons are always flying
around.
electron
•The Energy Levels
Atoms are usually represented as a nucleus
surrounded by rings.
• The rings are energy levels.
• The rings exist because e- can’t occupy random or the
same space at the same time.
• There are rules to how the e- are distributed.
• The row (going from top to bottom) tells you how
many rings the atom has.
•
•
•
Hydrogen is in the 1st row = one ring
Nitrogen is in the 2nd row = two rings
• Shown to the right.
•
•
How many rings does iodine have?
These are the atom’s energy levels.
•Reading the Periodic Table
• The
Column tells you how
many electrons in the outer
shell (valence electrons).
• The Row tells you how many
rings (Energy levels)
•The Outer Ring… The Valence Shell
Remember, electrons are orbiting the nucleus in the
region called the electron cloud... In different
energy levels (orbitals).
• The outer ring, called the valence shell, is the
important one.
•
• This
shows you the valence shell electrons.
• In the valence shell bonding happens.
•The Outer Ring
The outer most edges of this cloud is called the valence
shell.
• There is a strict rule for how many electrons are in this
valence shell.
• For most groups of atoms, you can determine the # of
valence shell electrons from the column it’s in.
•
•
•
•
•
•
•
The column determines the valence shell electrons.
Group 1A (hydrogen, etc.) has one valence electron.
Group 2A (beryllium, etc.) has two.
This rule only applies to A groups though.
How many valence electrons does phosphorus have?
A: 5
•Concept Check
• On
your handouts (back side of the periodic
table), complete the blank atom for the
element carbon.
•
Draw the:
• Correct
# of electrons
• Correct # of electron in the valence shell
• Correct # of protons
• Correct # of neutrons
•
Put them in the correct places.
•Representing the Atom
•Lots of Atom Models
• Which
one’s right?
• Depends on the application
•How do you show bonds?…
Lewis Dot Structures are best
Shows only symbol & the valence e- that participate
in bonding.
•Bohr’s
V.
Rutherford’s
-
-
-
-
+++
+++
-
+++
+++
-
-
-
-
-
-
Different Orbits
Same Orbit
•Where electrons actually are…Schrödinger
•
Q: Can you
identify
where the
electron
is?
+++
+++
•
A: No!
because
the
electrons
never stop
moving!
•Representing the Atom
• Bohr’s
•
Diagram
Shows the nucleus, all energy levels,
and electron distribution.
• Lewis
Structure
Shows the atomic symbol & valence e-.
• Shows the nucleus (with p+ & n0) plus
all inner energy levels (& electrons)
represented by the atomic symbol.
• Usually the easiest one to use.
•
•Practice. Create the Bohr & Lewis
Structure for…
• Oxygen
• Sodium
• Chlorine
• Uranium
•CW/HW Answers
Oxygen
Sodium
Chlorine
Tellurium
•CW/HW Answers
Oxygen
Sodium
Chlorine
Uranium
Sorry, bad example
•Chemical Bonds
•
•
Electrons in the valence shell are called valence electrons.
The number 8 is special.
•
•
•
•
•
•
This determines what atoms will bond with what.
Write this just above IX. Chemical Bonds
*OCTET RULE* (Generally speaking) Atoms tend to combine
with each other such that eight electrons will be in the valence
shell.
The reason is stability!
Regardless of the reason, when atoms are held together a force
called a chemical bond holds them.
There are three types of bonds that you need to know.
• Ionic bonds
• Covalent bonds
• Hydrogen bonds.
•Types
•
There are three types of bonds that you need to know.
• Ionic bonds = When atoms SWAP electrons creating ions
that attract.
• Covalent bonds = When atoms SHARE electrons to create
molecules.
• Hydrogen bonds = When polar molecules interact with
one another.
• There
is an order of strength…
• Covalent > Ionic > Hydrogen. (covalent is the strongest)
•Valence electrons: Do the Bonding
•Special Circumstance: Noble Gasses
• Some
atoms won’t bond with other elements
because they already have 8 valence
electrons.
• These are called Nobel Gasses.
• These are group 8A (all the way on the right).
•Chemical Bonds
• Every
other element will bond with other
elements to get to 8 valence electrons.
• Chemical bonds form between groups of
atoms because atoms become stable when
they have eight electrons in the valence shell.
• When atoms of different elements combine, a
compound forms.
• A compound is a substance made of the
bonded atoms of two or more elements.
•Common Compounds
• Ammonia
(NH3)
• Water (H2O)
• Methane (CH4)
• Glucose (C6H12O6)
• Salt (NaCl)
•Ionic Compounds
Ionic Bonding
• Atoms can sometimes achieve a stable valence level by
losing or gaining electrons.
• When this happens, the charge of the atom changes
slightly and an ion is formed.
•
[An ion is an atom or group of atoms that has an electric
charge because it has gained or lost electrons.]
Opposite charges attract.
• The attractive force between oppositely charged ions is
an ionic bond.
•
•How Do You Know How Many Electrons
Get Exchanged?
• It
is all based upon the number of valence
electrons for the element in its basic form.
• The metals on the left usually give electrons
because they are closer to 8 if they lose a few.
• The non-metals on the right usually gain
electrons because they will achieve 8 if they
gain just a few.
•Find These Elements on you Periodic Table
Gains eLoses e-
Carbon
Gains or
Loses eHow close are these elements to achieving 8 in their valence shell?
Is it faster to gain a few or lose a few?
The numbers of e- gained/lost are variable & correspond to how
many they need.
What about carbon?
•Complete B1 from handout. Formation of
Ions: Count the p+ & e- before & after the
exchange…
+
Na
Cl
Sodium
Before
After
Chlorine
Before
After
Protons
+11
+11
Protons
+17
+17
Electrons -11
-10
Electrons -17
-18
Total
+1
Total
-1
0
0
•How Do You Show the Bonds?
• Ionic
Bohr Model
Or…
Lewis Structure
We use Lewis Structures which only show the valence electrons.
•Show the bonding of Na with Chlorine
• Figure
out how many electrons sodium loses.
• How many does chlorine need?
• Find these and fill these out on your sheet.
-1 for sodiums
• +1 for chlorine
•
• Draw
the arrow showing the electron
moving.
Lewis Structure
•Example: MgI2
+2
I
I
• WHY?
-1
-1
Magnesium chloride.
(Just like B2): Since
Magnesium donated 2
electrons what should
its charge be?
Since each chlorine
received one electron
what should each
charge be?
+2
When Magnesium loses its
outer electrons it exposes
its next lower energy level,
which happens to have 8
electrons.
Cl
Cl
-1
-1
•Chemical Bonds, continued
Covalent Bonding
• One way that atoms bond is by sharing valence
electrons to form a covalent bond.
•
A molecule is a group of atoms held together by
covalent bonds.
•
A water molecule, H2O, forms when an oxygen atom
forms covalent bonds with two hydrogen atoms.
•Poor Oxygen…
•
•
•
•
•
Ah, I’m sad because my valence shell isn’t filled.
If there was only some way to get more.
Wait. Hey Buddy. If we shared some electrons, then we could both have
8…kinda.
Now we both can have eight!
Sometimes… and that’s enough to form a covalent bond.
•How Do You Show the Bonds?
• Covalent
Bohr Model
Lewis Structure
Or…
•Illustrate the bonding of 2H + O to make H2O
•2
minutes…
• How many electrons does oxygen need?
• How many does hydrogen need?
• How would these be shown in a bond?
Lewis Structure
•Example: C02
•Polarity
•
•
•
•
•
•
In some covalent molecules, the electrons are shared equally
between the atoms in the molecule.
In some covalent bonds, the shared electrons are attracted more
strongly to one atom than to the other.
It’s due to electronegativity (something you don’t need to know.
As a result, one end of the molecule has a partial negative
charge, while the opposite end has a partial positive charge.
Polar Molecules result when the resulting molecule has partial
charges on opposite ends because of electron motion and
average location.
Non polar molecules, like CO2,
•Same Atoms sharing electrons equally
Make it Non-Polar
-
-
-
-
-
-
+
+
-
-
-
-
•Not Sharing Electrons Equally Results in
Polar Molecules
-
-
Partially –
-
The electrons
spend more
time on this
side of water.
-
Partially +
The electrons
spend less time
on this side of
water
-
-
-
-
•Not Sharing Electrons Equally can sometimes
be 2 atoms, sometimes more.
-
-
-
-
Partially +
Partially -
-
•Hydrogen Bonding
•
A hydrogen bond is a
bond that forms
between the positive
hydrogen atom of one
molecule and the
negative pole of
another molecule.
Represented as
dashed lines.
We will see these
again…
•Polarity, continued
Hydrogen Bonds
• When bonded to an oxygen, nitrogen, or fluorine
atom, a hydrogen atom has a partial positive charge
nearly as great as a proton’s charge.
• It attracts the negative pole of other nearby
molecules.
• This attraction is stronger than attractions between
other molecules, but not as strong as covalent
bonds.
• However, hydrogen bonding plays an important role
in many of the molecules that make up living things.
•Polarity of Water
• Water
is a molecule that shares electrons
unequally.
• Oxygen attracts the electrons more than
hydrogen does.
• This causes the oxygen atom to be, on
average, more negative than the hydrogen,
which tend to be more positively charged.
2δ-
δ+
δ+
•Polar Molecules:
Water
The polarity of
water makes it
able to form
polar bonds
with other water
molecules,
called2δhydrogen
bonds,
due to
δ+
δ+
the negative
oxygen and the
positive
hydrogen.
•Atomic Models
• There
are a variety of ways to represent an atom…
• It really depends on why you are showing the
atom that will determine how you show it.
Electron-Dot Diagrams = show electrons & protons for
ions & bonding
• Space filling models = show how the molecule looks in
3D
• Bohr’s model = shows all electrons to represent
energy levels. WHAT YOU BUILT
• Lewis structures = shows valence electrons (only) for
bonding
•
•Concept Review
• What
are the three subatomic particles?
• Where are they located?
• Do electrons go anywhere they want?
• What is an isotope?
• What is an ionic bond?
• What is a covalent bond?
• What makes a molecule polar?
• Which is a Lewis structure & which is a
Bohr’s model?
•Why Bonding is Important?
• The
reason why we review bonding is
because the ability of atoms to interact with
each other allows for them to build larger
molecules.
• Depending on the types of numbers of atoms
an almost limitless number of molecules and
compounds can be formed, each with its own
unique properties.
• These build on one another to make life
possible.
•Practice
1.
2.
3.
Keep in mind, in an
ionic bond, electrons
leave one atom and
travel to the valence
shell of another.
Keep in mind, in a
covalent bond a pair of
electrons are
participating in the bond;
one from each atom.
4.
5.
6.
Draw Oxygen
Draw Phosphorus
Illustrate the ionic bonding
between sodium (Na) &
chlorine (Cl)
Draw the electrons (e-)
between hydrogen & oxygen in
H20
Illustrate the polarity of water
& draw the hydrogen bonding
between two water molecules.
2 minutes + check each.
•Group Practice
• Complete
the chart using your periodic table.
• 10 minutes.
•How do you show bonds?…
We will use Lewis Dot Structures
Shows only symbol & the valence e- that participate
in bonding.
•Illustrate the ionic bonding. 2 minutes each.
DON’T DO
DO
DO
DON’T DO
•Illustrate the covalent binding. 2 minutes each
DON’T DO
DON’T DO
DO
DO
•Now
• Get
into your groups.
• Together you will use your notes and books
to complete the worksheet so I know you
understand the basic concepts of bonding.
• We will cover the answers with 15 minutes
left in class so get busy and stay on task.
•Closure…
• Questions?
• What
did you learn today?
• Reflect in your warm ups…
•How to Represent an Atom.
• Standard
Electron Dot Diagram.
• Space-filling (O2)
• Bohr’s Model
• Lewis Structure
•Sample Questions: Self Quiz. Answers on the next slide.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
A(n) _________ is the smallest unit of matter that cannot be broken down by
chemical means.
Identify the 3 sub atomic particles of atoms and their locations in words or in an
illustration.
A(n) _________ is a substance made of only one kind of atom that has the same
number of protons.
Locate oxygen and tell me how many protons, neutrons, and electrons it has.
(use your periodic table…the atomic number is extremely useful).
Atoms are most stable when they have 8 electrons in their ______ ______.
How many protons, electrons, neutrons, energy levels, and valence electrons
does carbon have?
Name two ways that atoms can form bonds (combine to become more stable).
Describe polarity and a popular polar molecule.
Explain how polarity can cause salt & sugar to dissolve in water.
Water is an example of a compound that is held together by ________ bonds.
Atoms gain or lose ___________ to form ions.
The opposite ends of a polar molecule have ___________ charges.
A(n) _______ ______ is a weak chemical attraction between polar molecules.
•Answers
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
atom is the smallest unit of matter that cannot be broken down by
A(n) _________
chemical means.
Identify the 3 sub atomic particles of atoms and their locations in words or in an
illustration.
p+, e-, n0… p+, n0 in nucleus, e- in electron cloud
A(n)element
_________ is a substance made of only one kind of atom that has the same
number of protons.
8
8
8
Locate oxygen and tell me how many protons, neutrons, and electrons it has.
(use your periodic table…the atomic number is extremely useful).
valence _________.
shell
Atoms are most stable when they have 8 electrons in their __________
6
6
6
2
4
How many protons, electrons, neutrons, energy levels, and valence electrons
does carbon have?
Name two ways that atoms can form bonds (combine to become more stable).
Ionic (swapping electrons), covalent (sharing electrons) When a molecule has a partial + & partial –
Describe polarity and a popular polar molecule. charge. Water is polar and can dissolve the
ions & polar molecules in sugar & salt
Explain how polarity can cause salt & sugar to dissolve in water. because of polarity.
covalent bonds.
Water is an example of a compound that is held together by ___________
electrons to form ions.
Atoms gain or lose _______________
The opposite ends of a polar molecule have opposite
___________ charges.
bond is a weak chemical attraction between polar molecules.
A(n)hydrogen
__________ _________
•Quick Facts. Put an atom into perspective.
• If
you used a stadium to model and atom…
The Houston Astrodome (Home of the Houston
Astros…a baseball team) seats 60,000 fans, covers 9
acres and the dome rises to a height of 200ft.
++
• If you could blow up an +atom
to the size of this stadium
+++
a basketball could represent the volume of an atom's
nucleus.
• The rest of the open area is the volume of where the
electrons, maybe the size of tiny BB’s, would be
constantly flying around at speeds approaching the
speed of light through the electron cloud in their
orbitals.
•
•Atoms, continued
•
•
•
•
•
99+% of the atom’s mass is made up
of the protons and neutrons found in
the nucleus.
The other <1% of the atom’s mass is
found by adding up all the individual
electrons.
The nucleus takes up less than 1% of
the atom’s physical space… its
volume, however.
99+% of the atoms actual space is the
electron cloud where the electrons are
zooming around at nearly the speed
of light.
Technically, we are 99% empty space!
Electron Cloud
Nucleus
•Technically, We Are 99.9% Empty Space?
• Why
do we
appear solid?
•
•
Think about a plane propeller. Then image hundreds stacked on
top of each other.
Our skin is hundreds of cells thick, constructed of millions of
atoms each.
•Why Do Things Feel Solid?
We actually feel very little that is solid.
What we feel is the interpretation of what
solid is because of the electron clouds pushing
away from one another.