Download 2-1 Chemistry of life

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2-1 Chemistry of life
Objectives
• Define matter
• Explain the relationship between elements
and atoms
• Draw and label a model of the structure of
an atom
• Explain how compound affect an atom’s
stability
• Contrast covalent and Ionic bonds
Matter
• Matter: takes up
space, has mass
• Mass: how much of
something there is
• Element: simplest
form of matter
– Can’t be broken
down with chemical
means
– If you have a lump
of copper, boiling or
freezing doesn’t
change it
• There’s about 118 elements
•
•
When we total the monetary value of the elements in our bodies and the value
of the average person's skin, we arrive at a net worth of $4.50
Our most valuable asset is our skin. The method the Imperial State Institute for
Nutrition at Tokyo developed for measuring the amount of a person's skin is to take a
naked person, and to apply a strong, thin paper to every surface of his body. After
drying, its removed, cut it into small pieces, and the person's measurements are
totaled.The average person has fourteen to eighteen square feet of skin, (variables
being height, weight, and breast size). Based on the selling price of cowhide,(
approximately $.25/ square foot), the value of an average person's skin is about
$3.50.
•
On the other hand consider that urban legend of drugged travelers awaken in icefilled bathtubs only to discover one of their kidneys has been harvested by organ
thieves.
•
Though: in real life a small village in India was reportedly nicknamed Kidney Village
by national geographic writers because so many of its inhabitants had voluntarily sold
kidney’s for 800$ How much would you pay if you had to wait?
•
Now the question to ponder is this: Is the whole worth more than the sum of the
parts? If you put these these powdered elements together in a blender; how long
would you have to leave it on for to get a human?
•
How do these elements interact to make you who you are?
Dalton’s atomic theory
• All elements are made of atoms
• Atoms of the same element are identical
– Atoms of dif. Elements are dif.
• Atoms of different elements can combine
in whole number ratios to form compounds
• Reactions occur when atoms separate join
& rearrange
– Atoms them selves are never changed
• Whole number ratios are like two to one for H2O. Or one
two to three for Iron Sulfide Fe2S3
• Dalton’s born to a family of poor Quakers, Same city
William Wordsworth comes from, Bright guy, at the age
of 12 the put him in charge of the local school
• He was color blind and the world called it Daltonism for a
while. Of course not much can happen without
somebody objecting, in this case it was Ernst Mach (for
who we named the speed of sound)
• The theory came out in his 1808 book, and it was like
saying I’ve found a new planet. But he kept his job as a
teacher, and visiting scientists from around the world
would have to wait while he finished teaching math
class. Hugely popular, forty thousand people attended
his funeral in 1844.
Just how small is an atom?
• Small enough so that light will miss it
• 50 million atoms would fit side by side in a
1cm long groove so to speak.
• Scanning electron microscopes can view
the surface of atoms
Subatomic Particles
Particle
Symbol
Charge
Relative
Mass
Electron
e-
1-
0
Proton
p+
+
1
Neutron
n
0
1
Planetary Models of Elements
p+ represents protons, no represents neutrons
Atomic Number on the Periodic
Table
Atomic Number
Symbol
11
Na
Number of Electrons
 An atom is neutral
 The net charge is zero
 Number of protons = Number of electrons
 Atomic number = Number of electrons
Isotopes
 Atoms with the same number of protons,
but different numbers of neutrons.
 Atoms of the same element (same atomic
number) with different mass numbers
Isotopes of chlorine
35Cl
37Cl
17
17
chlorine - 35
chlorine - 37
Isotopes and Radioactivity
• Isotopes
– elements that differ in the number
of neutrons
•
1H, 2H, 3H;
hydrogen, deutrium,
tritium
– extra neutrons result in increased
atomic weight
• “heavy water”
– have no change in chemical
behavior
• same valence electrons
• Atomic weight
– Average atomic mass of the
mixture of isotopes of an
element found in a sample
Isotopes of Hydrogen
( 1p+, 0n0, 1e- )
( 1p+, 2n0, 1e- )
( 1p+, 1n0, 1e- )
Octet Rule
• Noble gases are stable because they have
just the right number of valence electrons.
• 2 for helium
• 8 for the rest
• This balances them eneregetically
• Octet Rule: all elements try to form bonds
so they have 8 valence electrons
– Some try to have just 2
Ions
• When an atom gains or loses an electron it takes
on a negative or positive charge
• If you gain an electron (negative energy) you have
a negative charge = Anion
– Plus a negative is subtraction
–
Cl-
• If you lose an electron (negative energy) you have
a positive charge = Cation
– Minus a negative is addition
–
Na+
Electrons can be transferred
• Sodium has 1 valence electron
• Chlorine has 7 valence
electrons
• How can Chlorine achieve the
octet?
– It gained an electron giving it a
negative charge
– It resembles a noble gas
• Did Sodium achieve the octet?
– It now resembles neon
• In Ancient Rome, salt
started to be used as
money originating the
current Latin-derivative
term salary.
• Payments to Roman
workers were made in
salt.
• Morton’s Salt: "When it
rains, it pours“
–
–
–
–
Owned by Rohm & Hass
#286 on fortune 500
7.99 Bil
They make all kinds of stuff
• Iodized Salt
Salt
Ions attract each other
• Opposites attract
• Ionic bonds between ions, they are trading
electrons.
• Ionic compounds have ionic bonds
– Crystals form
– Stable so they have high melting points
– Don’t bend
– Shatter
Electrons can be shared: Covalent
Bonds
• H2O is not ionic like
NaCl
• It becomes stable like
noble gases in a
different way.
• In water the Hs and O
share electrons
– It’s a different kind of
attraction
Covalent bonds
• Covalent compounds have covalent bonds
• 1 unit of a covalent compound is called a
molecule
– Sometimes they are called molecular
compounds
• They have lower melting points
• Examples: Water, Carbon Dioxide, Sugar,
Gasoline, Wax, Lighter fluid, propane
1. What is matter?
Anything that
has mass and
takes up space
2.
What is the
relationship
between elements
and atoms?
Elements are
substances that
can’t be broken
down into simpler
kinds of matter
Atoms are the smallest
particle of an
element that
retains all the
properties of that
element
3. Describe the
arrangement within
energy levels of the
six electrons in a
carbon atom.
Carbon will have 2
electrons in the first
energy level and
four electrons in the
second level
How many valence
electrons does
carbon have to
share with other
atoms?
4. How are isotopes
of the same
element alike?
They have the same
atomic number and
the same number of
protons.
5. How can we predict
which elements are
reactive under
normal conditions
and which are
unreactive?
Whether or not their
outer level of
electrons is filled.
6. Distinguish between ionic and covalent
bonds.
Covalent: Sharing electrons
Ionic: Trading electrons
7. Why are mass and
weight two
different terms?
Mass describes how
much matter is in
an element
Weight takes gravity
into consideration.
8. Element or compound?
HCl
CO2
Cl
Li
H2O