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Elements & Atoms
2.1
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An atom refresher
• Matter is anything that takes up space and has
mass.
• All matter is made of atoms
• Atoms are the building blocks of matter, sort of
how bricks are the building blocks of houses.
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An atom refresher
• An atom has three parts:
• Proton = positive
• Neutron = no charge
• Electron = negative
• The proton & neutron are
found in the center of the
atom, a place called the
nucleus.
Picture from
http://education.jlab.org/qa/atom_model_03.gif
• The electrons orbit the
nucleus.
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What are elements?
• Elements are the
alphabet to the language
of molecules.
• To make molecules, you
must have elements.
• Elements are made of
atoms. While the atoms
may have different
weights and organization,
they are all built in the
same way.
Information & picture from Chem4kids at
http://www.chem4kids.com/files/atom_structure.html
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Graphic from http://education.jlab.org/atomtour/fact2.html
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More about Elements..
• Elements are the building
blocks of all matter.
• The periodic table is a list of
all of the elements that can
build matter. It’s a little like
the alphabet of chemistry.
• The periodic table tells us
several things…
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Periodic Table
Atomic Number:
Number of protons
and it is also the
number of electrons
in an atom of an
Element’s Symbol:
element.
An abbreviation for
the element.
Elements Name
8
O
Oxygen
Atomic Mass/Weight:
Number of protons +
neutrons.
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16
• Atoms are made up of three particles:
 Protons
 Neutrons
 Electrons
• Question: Which of the three particles identifies
what element an atom is?
• The PROTON! (very important)
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Different Forms of the Same
Element
• In any element, the # of protons is always
constant.
• Unlike the number of protons, the number of
electrons and neutrons can vary within an
element without changing the identity of the
element.
 Ex. Carbon (C) ALWAYS has 6 protons, but it
can have anywhere from 6-8 neutrons and 2-10
electrons
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Isotopes
• An ISOTOPE is a form of an element that has a
different number of neutrons than “normal”
• Carbon has three isotopes
Atom Models
• There are several models of the atoms, we will
be using one in class.
• Lewis Dot Structure
Electrons have special rules….
• You can’t just shove all of the electrons into the
first orbit of an electron.
• Electrons live in something called shells or
energy levels.
• Only so many can be in any certain shell.
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Nucleus
1st shell
2nd shell
3rd shell
Adapted from http://www.sciencespot.net/Media/atomsfam.pdf
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Electrons have special rules….
• You can’t just shove all of the electrons into the
first orbit of an electron.
• Electrons live in something called shells or
energy levels.
• Only so many can be in any certain shell.
• The electrons in the outer most shell of any
element are called valance electrons.
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Chemical Compounds
• A chemical compound is two or more elements
combined together to form a “compound”
• Common compounds:
 Water (H2O)
 Salt (NaCl)
• The element proportion of the compound is
always the same Water is always H2O
regardless if it is a drop or a lake of water
• The compound properties are very different
from those of the element used to form them
Chemical Bonds
• Chemical bonds are what hold elements
together
• There are TWO main types of chemical bonds:
 IONIC
 COVALENT
Ionic Bonds
• Formed when one or more electrons are
transferred from one atom to another
• Remember that as a whole elements are
electrically neutral but if there is a movement of
electrons they can become positive or negative
• A charged element is called an ION
Covalent Bonds
• The sharing of electrons between two or more
atoms
• The electrons move between the nuclei of both
elements in the compound
• When covalent bonds are formed a molecule is
formed, it is the smallest unit of a compound
• Water is a covalent bond
Van der Waals Force
• The term given to intermolecular attraction of
molecules in close proximity to one another
• Water bugs 
So let’s try it…Lewis Dot
Structures
• How to draw a Lithium atom
• First, look at the Periodic Table
• Second, determine the number of
protons (Look @ the atomic number)
• Then determine the number of
neutrons (Atomic mass – atomic
number)
• Then determine the number of
electrons (Look @ the atomic number)
3
Li
Lithium
7
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So let’s try it….
Protons = 3
3
-
Li
+
+
+
Lithium
-
7
Electrons = 3
2 in the 1st shell, 1 in the 2nd shell
Neutrons = 4
(7-3=4)
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Lewis Dot Structure
• The Lewis Dot
Structure is a bit
different from the
Bohr model.
• It only shows the
element symbol
and it’s outer most
electron shell.
-
-
-
+
+ + +
-
-
+ + +
+
-
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-
•
• O ••
••
-
How to…
1. Write the
symbol.
2. Start on the
right hand side,
working your
way clockwise
around the
symbol.
3. Try Lithium
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Carbon Compounds
(2.3)
• Carbon bonds with a variety of elements, these
include:
 Hydrogen
 Oxygen
 Phosphorus
 Sulfur
 Nitrogen
• When carbon binds with these elements many
of molecules necessary for life are formed
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Macromolecules
• All organisms are composed of
macromolecules
• A macromolecule contains CARBON
• Most macromolecules are made of smaller units
(monomers) that bond to form larger molecules
(polymers)
• Energy is stored in the bonds that link these
units together. The process of bonding and
forming of macromolecules is polymerization
• The amount of energy stored varies with the
type of macromolecule formed.
Carbohydrates
• are molecules that are composed of Carbon,
Hydrogen, Oxygen
• Basic carbs are simple sugars
(monosaccharides) such as glucose , these
simple sugars can bond and create complex
carbs such as starches and cellulose
• Carbohydrates are the MAIN source of energy
for the cell
• When carbs are synthesized (created) during
photosynthesis the organisms that create them
use them as a source of energy or they are
stored in the cells. This process usually uses
monosaccharides to create polysaccharides
• When carbs are consumed, digestion breaks
the bond between large carbs (complex
carbohydrates: polysaccharides) so that
individual simple sugars can be absorbed by
the blood stream through intestinal walls.
Lipids
• are molecules that are composed of Carbon,
Hydrogen, Oxygen
• Are used in a variety of ways by living
organisms including:
 Energy storage
 Biological membranes
 Waterproof coverings
• Contain two component molecules , glycerols
and fatty acids so they are structurally different
from carbs
• Are NOT SOLUBLE IN WATER
• Have more carbon-hydrogen bonds than carbs
Nucleic Acids
• Contain : Hydrogen, oxygen, nitrogen, carbon
and phosphorus
• Are polymers comprised of a monomer known
as a nucleotide
• Nucleotide has:
 5 – carbon sugar
 Phosphate group
 Nitrogenous base
• Store and transmit hereditary (genetic)
information
Protein
• Molecules composed of chains of amino acids
(a.a.)
• A.A. are molecules that are composed of
Carbon, Hydrogen, Oxygen, Nitrogen and
occasionally Sulfer (CHONS)
• There are 20 a.a. that bond to make proteins
 12 a.a. are formed by the bodsy
 8 a.a. must come from foods
• Proteins have a variety of roles in organisms :
 Controlling rate of reactions
 Regulate cell processes
 Form cell structures
 Transport substances in and out of the cell
 Fight disease
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Organizational levels of proteins
• When amino acids (a.a.) are assembled the
instructions come from the DNA
• There are 4 levels of protein structures
 Primary : chain of amino acids
 Secondary: folding of chain
 Tertiary: 3-d arrangement of amino acids
 Quaternary: is the combination of more than one
chain (hemoglobin)
THE NUTRITION LABEL
Easy Ways to Use the Label
For Healthy Eating
For more information, please contact:
Food and Drug Administration
Center for Food Safety and Applied Nutrition
Office of Nutritional Products, Labeling, and Dietary Supplements
Key Label Questions
• How many calories am I actually eating? Is that number
low, medium, or high?
• What nutrients should I limit or get enough of and why?
• What’s relevant about the footnote?
• How can I tell if a %DV is high or low?
• Which nutrients have no %DV?
The Nutrition Facts Label
One or Two Servings?
Serving Size
Calories
Calories from Fat
Total Fat
Trans Fat
Saturated Fat
Cholesterol
Sodium
Total Carbohydrate
Dietary Fiber
Sugars
Protein
Vitamin A
Vitamin C
Calcium
Iron
Single
Serving
1 cup (228g)
250
110
12g
1.5g
3g
30mg
470mg
31g
0g
5g
5g
%
DV
18%
15%
10%
20%
10%
0%
4%
2%
20%
4%
Double
Serving
2 cups (456g)
500
220
24g
3g
6g
60mg
940mg
62g
0g
10g
10g
%
DV
36%
30%
20%
40%
20%
0%
8%
4%
40%
8%
General
Guide to Calories*
40 Calories is low
100 Calories is moderate
400 Calories is high
*Based on a 2,000-calorie diet.
Limit These Nutrients
The goal is to stay
BELOW 100% of the
DV for each of these
nutrients per day.
Get Enough of These Nutrients
Try to get 100% of the
DV for each of these
nutrients each day.
The Footnote
Examples of DVs versus %DVs*
The Percent Daily Value
The % DV is based on
100% of the daily value
for each nutrient.
What’s High? What’s Low?
Do You Have to Calculate to
Know?
Footnote
The % DV Does the Math for You
Look here for highs
and lows!
Quick Guide to %
DV
5% DV or less is Low
Limit these
Nutrients
Get Enough
of these
Nutrients
20% DV or more is High
No % Daily Value
• Trans Fat
• Sugars
• Protein
Read the Nutrition Facts Label
For Total Sugars
Plain Yogurt
Fruit Yogurt
Look at the Ingredient List
for Added Sugars
Plain Yogurt
INGREDIENTS: CULTURED PASTEURIZED GRADE A NONFAT MILK,
WHEY PROTEIN CONCENTRATE, PECTIN, CARRAGEENAN.
Fruit Yogurt
INGREDIENTS: CULTURED GRADE A REDUCED FAT MILK, APPLES,
HIGH FRUCTOSE CORN SYRUP, CINNAMON, NUTMEG, NATURAL
FLAVORS, AND PECTIN. CONTAINS ACTIVE YOGURT AND L.
ACIDOPHILUS CULTURES
Calcium In Your Daily Diet
Calcium
Calcium Calculation
100% DV = 1,000mg calcium
30% DV = 300mg calcium = one cup of milk
130% DV = 1,300mg calcium = daily goal for teens
For More Information
www.cfsan.fda.gov/~dms/labgen.html
• Guidance on How to Understand and Use the
Nutrition Facts Panel on Food Labels
(also available in Spanish)
• Test Yourself! Test Your Food Label
Knowledge!
• Food Label Education Video
• Calcium! Do You Get It?
Properties of Water
2.2
•
http://www.visionlearning.com/library/flash_viewer.php
?oid=1349&mid=55
• http://web.visionlearning.com/custom/chemistry/ani
mations/CHE1.7-an-H2Obond.shtml
I. Properties of Water
• Single most abundant compound in living things
• Liquid at the temperatures found over much of
Earth’s surface
• Expands as it freezes- ice is less dense than
liquid water- ice floats
a. The Water Molecule
 Overall it is neutral
• Polar: molecule in which charges are unevenly
distributed
 Protons attract electrons
 In a molecule the atom with more protons has a stronger
hold on the electrons
• Protons give them POWER
• H2O: Oxygen has 8 protons
Hydrogen has 1 proton
Who has the POWER (the electrons)?
Which end is positive? Which end is negative?
• Location of Electrons: around O
• Charge of O end: (-)
• Charge of H end: (+)
Hydrogen Bonds
• One of Van der Waals Forces
• Attraction between the H+ atom of one
molecule and the O- atom of another molecule
• Water can form 4 hydrogen bonds
Cohesion
• SAME substances
• Why drops of water
form beads.
• Why insects can
walk on water
Adhesion
• DIFFERENT
substances
• Why a meniscus
forms in a graduated
cylinder
• Why water moves up
against gravity in
tubes and the roots
of plants- Capillary
Action
Capillary Action
• Adhesion between water and glass
• Causes water to rise up a narrow tube against
gravity
 Water rises out of the roots of a plant and up into
its stems and leaves
 Meniscus in a graduated cylinder- water is higher
next to the glass sides, water moves up the
sides
Mixtures Made With Water
• Mixture: 2 or more elements/compounds that are
physically mixed together NOT chemically
• Solutions: evenly distributed throughout, dissolved in
water
 Salt water and sugar water
 Solute: substance being dissolved, SALT
 Solvent: substance doing the dissolving, WATER
 Polar water can dissolve both ionic compounds and other
polar molecules
• Suspension: suspended in water, NOT dissolved, so
small they are carried along by the water
 Oil and water
Acids, Bases and pH
• H2O↔
H+
+
OH-
Water ↔ hydrogen ion + hydroxide ion
• pH
 Indicator of the concentration (amount) of H+
ions
 Scale ranges from 0 to 14
 Each step on the scale represents a factor of 10
Neutral
Acid
Base
Pure Water
Compound
that forms H+
ions in
solution
# of H+ > # of OH-
Compound
that forms
OH- ions in
solution
# of H+ < # of OH-
pH 0 to 6
pH 8 to 14
# of H+
pH 7
=
# of OH-
Buffers
• pH of cells needs to be between 6.5 and 7.5
• Used to keep the pH at this level
• Weak acids and bases
• React with strong acid/bases to prevent sudden
changes of pH in the body
ENERGY IN REACTIONS
• Energy is released or absorbed whenever
chemical bonds are formed or broken.
• Because chemical reactions involve breaking
and forming of bonds, they involve changes in
energy.
CATALYST
• A catalyst is a
substance that
speeds up the rate of
a chemical reaction.
• Catalyst work by
lowering reaction’s
activation energy.
NOTICE THAT WITHOUT THE ENZYME IT TAKES A LOT MORE
ENERGY FOR THE REACTION TO OCCUR. BY LOWERING THE
ACTIVATION ENERGY YOU SPEED UP THE REACTION.
ENZYMES
• Enzymes are proteins that act as biological
catalysts.
• Cells use enzymes to speed up chemical
reactions that take place in cells.
• Enzyme speed up reactions by lowering the
activation energies.
• Because a particular enzyme catalyzes only
one reaction, there are thousands of
different enzymes in a cell catalyzing
thousands of different chemical reactions
NOTE
Enzymes end in
ase
Catalase
lactase
ENZYMES
• Enzymes provide a
site where reactants
can be brought
together to react.
• Such a site reduces
the energy needed for
a reaction to occur.
ALL ENZYMES HAVE AN ACTIVE
SITE, WHERE SUBSTRATES ARE
ATTRACTED TO.
• Enzymes are used over and over again.
SUBSTRATE
• The substance
changed or acted
upon by an enzyme is
the substrate.
THE ENZYME SUBSTRATE COMPLEX
• When enzymes function
the active site interacts
with the substrate.
• The active site shape
matches the substrates
shape. (like a lock and
key)
• Once the substrate and
active site meet a change
in shape of the active site
causes a stress that
changes the substrate
and produces an end
product.
WHICH ONE WILL FIT ?
WHY ENZYMES?
• http://www.youtube.com/watch?v=XTUm-75PL4&feature=related
THE FACTORS THAT AFFECT
ENZYME ACTIVITY ARE
• pH
• Temperature
• Amount of substrate
AFFECTS OF TEMPERATURE
ON AN ENZYME
• If temp to high or to
low the enzyme will
not fit. No reaction will
occur.
HOW PH AFFECTS AN ENZYME
• If the pH is to high or
low the enzyme will
not work, because its
shape will change.
PH
• All enzymes have an
optimum pH that they
function best at.
• If the pH is too low or
too high the enzyme
will work slow because
the change in pH
changes the shape of
the enzyme making it
harder for the
substrate to fit in.
ANALYZE THE GRAPH AT WHAT
PH DOES CHYMOTRYPSIN
FUNCTION BEST?
TEMPERATURE
• Enzymes function best at
an optimum temperature
depending on the type of
enzyme it is.
• As the temperature rises
the enzyme and substrate
molecules move quicker
causing more collisions to
occur, there for creating
more products.
• If you make the
temperature to high you
will destroy the protein
(denature) it.
WHAT IS THE OPTIMAL TEMP
FOR THIS ENZYME
AMOUNT OF SUBSTRATE
PRESENT
• At low substrate
concentrations, collisions
between enzymes and
substrate molecules are
rare and reactions are
slow.
• As the amount of
substrates increase so
does the collisions
between enzymes and
substrates.
• This continues until the
enzymes are saturated.