Transcript Chapter 2 Quiz

Chapter 2 Quiz
1.
One of the four most common elements in living
organisms is?
2.
What trace element is commonly added to table
salt to prevent goiters?
3.
Chemical bonds are formed by the interaction of
which subatomic particle?
4.
What type of bonds are important in the ability of
water to regulate temperature?
5.
Is a solution with a pH of 2 more acidic than a
solution a pH 7?
Ch. 2
The Chemical Basis of Life
I.
Elements and Compounds
A. Most common and trace
elements
II. Subatomic particles
A. Radioactive isotopes
B. Placement of electrons in shells a
III. Bonds bind together compounds
through electron interactions
A. Single, double, covalent, ionic,
polar, nonpolar, hydrogen
V. Acids and Bases
IV. Chemical reactions
A. How to write a chemical reaction
Elements and Compounds
• Everything around us is made of chemicals – these
may be in two forms
–
An element is a substance that cannot be broken down to
other substances by chemical reactions
–
A compound is a substance consisting of two or more
elements in a fixed ratio
• A compound has characteristics different from those
of its elements
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Organization of the periodic table
Periodic table of the elements
Organization of the periodic table
Periodic table of the elements
Periodic table of the elements
Most common elements in the human body
Table 2-1
Subatomic particles
• Neutrons (neutral) and protons (+)form the
atomic nucleus
• Electrons (-) form a cloud around the nucleus
Atomic Number and Atomic Mass
•
•
•
•
Atoms of the various elements differ in number of subatomic particles
An element’s atomic number is the number of protons in its nucleus
An element’s mass number is the sum of protons plus neutrons in the nucleus
Atomic mass, the atom’s total mass, can be approximated by the mass number
What element is this?
Is it electronically
neutral or charged?
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Atomic Number and Atomic Mass
•
•
•
•
Atoms of the various elements differ in number of subatomic particles
An element’s atomic number is the number of protons in its nucleus
An element’s mass number is the sum of protons plus neutrons in the nucleus
Atomic mass, the atom’s total mass, can be approximated by the mass number
What is the atomic number? Mass number?
How many protons, neutrons or electrons does
this element have?
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What element is this? What is the atomic number? Mass number? How
many protons, neutrons or electrons does this element have?
Question
• Points to remember
– Protons + neutrons = mass number
– Protons = atomic number
– Uncharged atoms have the same number of
protons and electrons
• An uncharged atom of carbon has an atomic
number of 6 and an atomic mass of 13. How
many electrons does carbon have?
Reviewing concepts
 Elements differ in their
number of protons,
neutrons, and
electrons
 Helium has two
protons, two neutrons,
and two electrons
 Carbon has six
protons, six neutrons,
and six electrons
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Reviewing concepts
Electron
cloud
Nucleus
2
Protons
2
Neutrons
2
Electrons
2e–
Mass
number = 4
2.4 Atoms consist of protons, neutrons, and
electrons
 Although all atoms of an element have the same
atomic number, some differ in mass number
– The variations are isotopes, which have the same
numbers of protons and electrons but different numbers
of neutrons
– One isotope of carbon has 8 neutrons instead of 6 (written
14C)
– Unlike 12C, 14C is an unstable (radioactive) isotope that gives
off energy
– A radioactive isotope is an isotope that
decays
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Mass Extinction
Time Line
Jurassic
Dinosaurs dominate
Cretaceous
Become extinct
Mammals begin to dominate
How have scientists formed this timeline?
2.5 Radioactive isotopes can help or harm us
 Living cells cannot distinguish between isotopes of
the same element
1. Therefore, when radioactive compounds are used in
metabolic processes, they act as tracers
2. Radioactivity can be detected by instruments
 With instruments, the fate of radioactive tracers
can be monitored in living organisms
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Fig. 2-7
Cancerous
throat
tissue
2.5 Radioactive isotopes can help or harm us
 In addition to benefits, there are also dangers
associated with using radioactive substances
– Uncontrolled exposure can cause damage to some
molecules in a living cell, especially DNA
– Chemical bonds are broken by the emitted energy,
which causes abnormal bonds to form
– Chernobyl-Apart from the 57 direct deaths in the
accident itself, UNSCEAR originally predicted up to
4,000 additional cancer cases due to the accident
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Radioactivity can be good or bad
“Natural” can be good or bad
 The dangers posed by certain chemicals in our food and
broader environment often lead people to associate
chemicals with harm. People might not want chemicals
added to their food or in their environment
 Chemicals both natural and artificial are made of the same
elements
 Naturally occurring toxins
 Tetanus
 Botulinum
 As mentioned before with ginko biloba herbal supplements
are unregulated by FDA
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2.2 Trace elements are common additives to food
and water
 Several chemicals are added to food for a variety
of reasons
1. Help preserve it
2. Make it more nutritious
3. Make it look better
 Check out the “Nutrition Facts” label on foods and
drinks you purchase
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2.2 Trace elements are common additives to food
and water
Ex. Good additive
A Goiter in a Malaysian woman, a symptom of iodine
deficiency.
2.2 Trace elements are common additives to food
and water
Video1
Video2
More additives
Ex. Iron
Quiz 1 1.
2.
What type of cell contains a nucleus, prokaryotic or eukaryotic?
Of the following options, list which ones are consistent with
Darwin’s theory of evolution.
a. Natural selection can lead to the appearance of new species.
b. Natural selection ensures that the organism that is most adapted to its
environment will live to pass on its genes.
c. Individual organisms exhibit genetic change during their life spans to better fit
their environment.
d. Natural selection is based in part on the overproduction of offspring.
e. Individuals in a population exhibit variations, some of which are heritable.
3.
T/F A controlled experiment will have at least two groups. One is
called the experimental group which will be compared to the
control group.
4.
Of the three domains discussed, name one domain that contains
prokaryotes.
5.
T/F A fungus kills 99% of a daisy population. You would expect
the next generation of daisies to be more resistant to the fungus.
6.
Name one of the four most common elements in living organisms.
7.
Which of the following is not found in the nucleus of an atom.
Proton, neutron, electron.
2.6 Electron arrangement determines the
chemical properties of an atom
 Only electrons are involved in chemical activity
 Electrons occur in energy levels called electron
shells
– Information about the distribution of electrons is found
in the periodic table of the elements
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Hydrogen
Helium
First
shell
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
Silicon
Phosphorus
Sulfur
Chlorine
Argon
Second
shell
Sodium
Third
shell
Magnesium Aluminum
2.6 Electron arrangement determines the
chemical properties of an atom
 An atom may have one, two, or three electron
shells
– The number of electrons in the outermost shell
determines the chemical properties of the atom
– The first shell is full with two electrons, whereas the
second and third will hold up to eight electrons
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2.6 Electron arrangement determines the
chemical properties of an atom
 Atoms want to fill their outer electron shells
1. To accomplish this, the atom can share, donate, or
receive electrons
2. This results in attractions between atoms called
chemical bonds
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Hydrogen
Helium
First
shell
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
Silicon
Phosphorus
Sulfur
Chlorine
Argon
Second
shell
Sodium
Third
shell
Magnesium Aluminum
All elements have an innate desire to have a filled
valence shell
 How many electrons does the first shell hold? Second? Third?
 Because elements want to have a completely filled valence
shell they will react with other elements to accomplish this
 Some elements have electrons to donate or share others are on
the receiving end of things
 In the end the elements will come together to form a
compound
 Compounds are always formed through the interactions of
electrons between two different elements
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Types of chemical bonds to know
It is imperative that you completely understand 2.6-2.10- hint, hint
 Bonds are interactions of electrons between atoms
that result in them staying close together
 Covalent
 Ionic
 Single
 Double
 Polar
 Nonpolar
 Hydrogen
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Types of chemical bonds to know
 Bonds are interactions of electrons between atoms
that result in them staying close together
 Covalent
 Ionic
 Single
 Double
 Polar
 Nonpolar
 Hydrogen
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Types of chemical bonds to know
 Bonds are interactions of electrons between atoms
that result in them staying close together
 Covalent
 Ionic
 Single
 Double
Sharing of
electrons
 Polar
 Nonpolar
 Hydrogen
Water is another example of
covalent bonds
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Question
 A hydrogen atom contains one electron. How many
covalent bonds can it form?
Types of chemical bonds to know
 Bonds are interactions of electrons between atoms
that result in them staying close together
 Covalent
 Ionic
 Single
 Double
 Polar
 Nonpolar
 Hydrogen
Atoms strip electrons from their
bonding partners, resulting in both
atoms having a charge (ions)
NO SHARING as in covalent bonds
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Types of chemical bonds to know
 Bonds are interactions of electrons between atoms
that result in them staying close together
 Covalent
 Ionic
 Single – represented by one line (H-H), one pair of
electrons is shared
 Double – represented by two lines (O=O), two pairs of
electrons are shared
 Polar
Single bond
 Nonpolar
 Hydrogen
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Double bond
Types of chemical bonds to know
 Bonds are interactions of electrons between atoms
that result in them staying close together
 Covalent
 Ionic
 Single
 Double
 Polar
 Nonpolar
 Hydrogen
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Electronegativity
• Electronegativity is an atom’s attraction for
the electrons in a covalent bond
• The more electronegative an atom, the more
strongly it pulls shared electrons toward itself
• Electronegativity is the cause of polar bonds
• Oxygen is very electronegative
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• In a nonpolar covalent bond, the atoms
share the electron equally
• In a polar covalent bond, one atom is
more electronegative, and the atoms do
not share the electron equally
• Unequal sharing of electrons causes a
partial positive or negative charge for each
atom or molecule – giving the compound
two opposite “poles”
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Important Example
(–)
O
H
(+)
H
H2O
(+)
Oxygen is greedy for electrons and doesn’t share well.
Oxygen is more electronegative than hydrogen. It pulls
the electrons of the covalent bond.
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2.9 Unequal electron sharing creates polar
molecules
 In molecules of only one element, the pull toward
each atom is equal, because each atom has the
same electronegativity
1. The bonds formed are called nonpolar covalent
bonds
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2.9 Unequal electron sharing creates polar
molecules
 Water has atoms with different electronegativities
– Oxygen attracts the shared electrons more strongly
than hydrogen
– So, the shared electrons spend more time near oxygen
– The result is a polar covalent bond
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2.9 Unequal electron sharing creates polar
molecules
 In H2O the oxygen atom has a slight negative
charge and the hydrogens have a slight positive
charge
1. Molecules with this unequal distribution of charges are
called polar molecules
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(–)
(–)
O
H
(+)
H
(+)
Types of chemical bonds to know
 Bonds are interactions of electrons between atoms
that result in them staying close together
 Covalent
 Ionic
 Single
 Double
 Polar
 Nonpolar
 Hydrogen – ex. results from the attraction between the
partial positive charge on the hydrogen atom of water and
the partial negative charge on ammonia, hydrogen bonds
are weak interactions
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2.10 Hydrogen bonds are weak bonds important
in the chemistry of life
 Some chemical bonds are weaker than covalent
bonds
 Hydrogen, as part of a polar covalent bond, will
share attractions with other electronegative atoms
1. Examples are oxygen and nitrogen
 Water molecules are electrically attracted to
oppositely charged regions on neighboring molecules
– Because the positively charged region is always a
hydrogen atom, the bond is called a hydrogen bond
Animation: Water Structure
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Hydrogen bond
Hydrogen bond
Water molecules stick to other water
molecules because hydrogen bonds
form between the hydrogen atoms of
one water molecule and the oxygen
atoms of other water molecules.
Water’s life supporting properties
•
Four fabulous
properties of water
that facilitate life as
we know it:
–
Cohesive behavior –
surface tension
–
Ability to moderate
temperature
–
Expansion upon freezing
–
Versatility as a solvent
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2.15 The chemistry of life is sensitive to acidic
and basic conditions
 A few water molecules can break apart into ions
– Some are hydrogen ions (H+)
– Some are hydroxide ions (OH–)
– Both are extremely reactive
– A balance between the two is critical for chemical processes
to occur in a living organism
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pH
• Water is in a state of dynamic equilibrium in which water
molecules dissociate at the same rate at which they are
being reformed
• H2O  H+ + OHHydrogen ion
Hydroxide ion
• In neutral water, they are present in equal concentrations.
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Acids and Bases
• An acid is any substance that increases the H+
concentration of a solution
– HCl  H+ + Cl-
• A base is any substance that reduces the H+
concentration of a solution
– NaOH  Na + + OH- *
*
The hydroxide ion will react with the H+ ions in the solution to
create water, in this reaction it will indirectly reduce the H+
concentration of a solution
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See-saw of ions
OHH+
Acid: low pH
H+
OH-
Neutral
H+
OH-
Base: high pH
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pH
Acid
Base
Less than 7
Greater than 7
[H+] increases
decreases
How are all of these bonds formed and then
broken?
 Chemical reactions are the making and breaking of chemical bonds
 The starting molecules of a chemical reaction are called reactants
 The final molecules of a chemical reaction are called products
Chemical reactions occur all the time all around us. Rusting of a car, cooking a
meal, burning a fire, running your car on gasoline.
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2.16 CONNECTION: Acid precipitation and
ocean acidification threaten the environment
 When we burn fossil fuels (gasoline and heating
oil), air-polluting compounds and CO2 are released
into the atmosphere
– Sulfur and nitrous oxides react with water in the air to
form acids
– These fall to Earth as acid precipitation, which is rain,
snow, or fog with a pH lower than 5.6
– Additional CO2 in the atmosphere contributes to the
“greenhouse” effect and alters ocean chemistry
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Consider the statement:
“It’s paranoid and ignorant to worry about industry or agriculture
contaminating the environment with their chemical wastes. After all,
this stuff is just made of the same atoms that were already present
in our environment anyway.”
What do you think of this statement?
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