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Environmental Science
Matter
• Anything that has mass and takes up space
• Solid, liquid, gas
Energy
• Does not take up space, no mass
• Definition: Ability to do work
Light
Heat
Electricity
Element
• Pure substance that cannot be broken down by
ordinary chemical means
• There are over 100 elements, below are the ones you
will need to know.
Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus
Sulphur
Sodium
Potassium
Fluorine
Chlorine
Calcium
Iron
Mercury
Lead
Element
• Each element has a name and a 1-2 letter symbol.
• The symbols are often the first letter of name or first letter
and one additional.
• Some symbols are based on latin names - e.g. natrium
instead of sodium, ferrium instead of iron, plumbum instead
of lead.
Carbon
C
Hydrogen H
Oxygen
O
Nitrogen N
Phosphorus P
Sulphur
S
Sodium
Potassium
Fluorine
Chlorine
Calcium
Iron
Na
K
F
Cl
Ca
Fe
Mercury Hg
Lead
Pb
Compound
• Substance that can be broken down by
ordinary chemical means
Water --> Hydrogen and Oxygen
Sugar --> Carbon & Oxygen & Hydrogen
Element
• Elements are composed of atoms.
• Different elements have different atoms.
Carbon
C
Hydrogen H
Oxygen
O
Nitrogen N
Phosphorus P
Sulphur
S
Sodium
Potassium
Fluorine
Chlorine
Calcium
Iron
Na Mercury Hg
K Lead
Pb
F
Cl
Ca
Fe
Atom
• Smallest particle of an element that has identity of
element.
• Composed of subatomic particles:
• protons - positive charge
• electrons - negative charge, much
smaller than protons
• neutrons - no charge, similar in
size to protons
Atom
• Protons and neutrons occur in center of atom in
region termed nucleus.
• Below is a oxygen nucleus with 8 protons and 8
neutrons.
• Different elements have different numbers of
protons and neutrons in the nucleus.
Nucleus
Atom
•
Electrons occur outside
the nucleus in regions
called shells
• The 1st shell holds 2
electrons.
• The 2nd shell holds 8
electrons.
• The 3rd shell holds 8
electrons.
Oxygen
Atom
• Different elements have
different numbers of
electrons.
• In neutral atoms, the
number of electrons =
the number of protons.
• Oxygen has 8 electrons.
Oxygen
Atom
• When placing electrons
in shells, put the first 2
electrons in the first
shell. They occur as a
pair.
Atom
• Then add electrons to
the 2nd shell.
• The 2nd shell has 4
regions.
• Put electrons
individually in the 4
areas and then start
pairing.
• Observe the order in
the next several slides.
Atom
• 3rd electron goes in
2nd shell
Atom
• 4th electron goes in
next area of 2nd shell
Atom
• 5th electron goes in
next area of 2nd shell.
Atom
• 6th electron goes in
next area of 2nd shell
Atom
• When each of the 4
areas has one
electron, then the
electrons pair.
• 7th electron pairs with
3rd.
Oxygen Atom
• 8th electron pairs with
4th.
• Oxygen has only 8
electrons so we stop
here.
• Larger atoms have
more electrons to fill
this shell and then
continue to 3rd shell
which also has 4 areas.
Sodium Atom
•Sodium has 11 protons, 12 neutrons and 11
electrons.
•The 11 protons and 12 neutrons go in the central
nucleus.
Sodium Atom
• Put first 2 electrons in first shell (paired).
Sodium Atom
• Then add electrons to second shell.
Sodium Atom
• Then add electrons to second shell.
Sodium Atom
• Then add electrons to second shell.
Sodium Atom
• Then add electrons to second shell.
Sodium Atom
• Then add electrons to second shell.
Sodium Atom
• Then add electrons to second shell.
Sodium Atom
• Then add electrons to second shell.
Sodium Atom
• Then add electrons to second shell.
Sodium Atom
• When 2nd shell is full, add third shell.
• Sodium has 11 electrons, so only 1 electron in 3rd
shell.
Periodic Table
• The periodic table shows the elements and
their symbols.
• It gives info on the numbers of protons,
neutrons and electrons.
• The atomic number is the number of protons.
All atoms of that element have that number of
protons.
• The atomic weight is the mass of the atom and
indicates the number of protons, neutrons and
electrons.
Periodic Table
Atomic Number = # protons
Periodic Table
Atomic Weight
Atomic Weight
• The atomic weight is the mass of the
protons, neutrons and electrons.
8
Oxygen
O
15.9994
• Since electrons have little mass, the atomic
weight tells us the number of neutrons.
• For example, Oxygen has an atomic number
of 8 and atomic weight of 15.9994 = 16.
• 8 is the number of protons.
• Neutrons = 16 - 8 = 8
• Neutrons are similar in number to protons
but not always the same.
Isotopes
• Atoms with the same number of protons but different
number of neutrons. (The number refers to the
weight.)
C12
6 protons, 6 neutrons
C14
6 protons, 8 neutrons
Isotopes
Uranium
235
Uranium
238
92 protons
143 neutrons
92 protons
146 neutrons
• Uranium is used in nuclear power.
• U238 is the most common isotope.
• U235 is needed for nuclear power so mined Uranium is
processed before use to get a higher percentage of
U235. This is called enrichment.
Theory
• Scientific statement with high degree of
certainty
• Supported by many observations and tests
Atomic Theory
• Matter is composed
of atoms
Ions
•Charged particles.
• The number of protons does not
equal the number of electrons.
•Recall that electrons are on outer
part of atom and protons are in
central nucleus.
•It is electrons that are gained or lost
to form ions.
•Protons do not change.
Neutral Sodium Atom
11 protons
11 electrons
0 charge
Sodium Ion
11 protons
10 electrons
+1 charge
Sodium Ion
Symbol
Na +
•Note the charge is
indicated by a
superscript.
•The + indicates +1
Sodium Ion
Na
+
•Note that the
outermost shell
with electrons is
full.
•This is a stable
condition.
•Atoms form ions
so that outermost
shell is full.
•Sodium ion is
common and
stable.
Neutral Chlorine Atom
17 protons
17 electrons
0 charge
17 +
18 0
Chloride Ion
17 protons
18 electrons
-1 charge
17 +
18 0
Chloride Ion
Cl
• Note that the
17 +
18 0
outermost shell
with electrons is
full.
• The - subscript
indicates a -1
charge.
Molecules
• 2 or more atoms or ions bonded together
Na+
Cl-
Ionic Bond
Electrical Attraction
between ions
NaCl = Table Salt
O
H
Covalent Bond
Atoms Share Electrons
Water
H2O
O
H
•
•
•
•
H
Consists of 1 oxygen and 2 hydrogen atoms
Has 2 covalent bonds
Symbolized H2O
The 2 as subscript indicates the number of atoms.
Common Molecules
H2O
Water
O
H
O
H
C
O
CO2
Carbon Dioxide
NH3
N
H H
Ammonia
H
O O
O2
Oxygen Gas
Molecules
N2
N
N
CH4
H
C6H12O6
glucose
Nitrogen Gas
H
C
H
Methane Gas
H
Chemical Reactions
• Molecules are rearranged to form new molecules
Start
“Reactants”
H2O
O2 + H2
Finish
“Products”
• Note: This reaction is used to make hydrogen gas
for fuel cells, an alternate fuel source.
Chemical Reactions
• Molecules are rearranged to form new molecules
C6H12O6 + O2
CO2 + H2O
N2 + H2
light
CO2 + H2O
C6H12O6 + O2
NH3
Respiration
Photosynthesis
Nitrogen Fixation
Acid and Base
•
Acid - Molecule that breaks down in water to form H+
Hydrochloric Acid HCl
H+ +
Cl-
HNO3
H+ +
NO3-
Nitric Acid
• Base - Molecule that breaks down in water to
form OHSodium Hydroxide
NaOH
Na+ + OH-
pH
•
• Based on log scale
Measure of H+ concentration
( pH = -log [H+] )
1 2 3 4 5 6 7 8 9 10 11 12 13 14
neutral
acid
base
pH 1 means H+ concentration is 10-1 or .1
pH 7 means H+ concentration is 10-7 or .0000001
Thus pH 1 is more acidic than higher pH 7.