Transcript academic biology basic chemistry notes

ACADEMIC BIOLOGY
BASIC CHEMISTRY
NOTES
ATOMS
A.
B.
An atom is the smallest particle of an
element.
Arrangement
1.
2.
3.
4.
Nucleus – The center of an atom.
Proton – (+) charged particle found
inside the nucleus.
Electron – (-)charged particle found
outside the nucleus.
Neutron – Particle found in the nucleus
with no charge.
C. Energy Levels
1.
Regions where electrons travel around the
nucleus.
2.
Each energy level can only hold a certain
number of electrons.
a. The first energy level can hold 2 electrons.
b. The second energy level can hold 8 electrons.
c. The third energy level can hold 18 electrons.
3.
All energy levels being used must be full for
an element to be stable.
Example:
If an element has 8 total electrons, 2 will be in the first
energy level and the remaining 6 will be in the second.
Is it stable?
Electron Configuration Examples:
1. Draw the electron configuration for an atom
with 10 electrons. Is it stable?
2. Draw the electron configuration of an atom with
16 electrons. Is it stable?
ELEMENTS
A. A substance which cannot be broken
down into simpler substances.
1.
There are 90 naturally occurring
ones in nature.
B. All elements are listed on the Periodic
Table.
Elements
• Only 25 elements are needed for
living things.
• 96% of the mass of a human being is
composed of C,H,N and O.
D. Atomic Number
E. Atomic Mass
1. The number found
above an element on
the periodic table.
a. Is equal to the
total protons in a
nucleus.
b. Also indicates the
number of
electrons since
protons and
electrons always
equal one another.
1. The number found
below an element on
the periodic table.
a. Is equal to the total
protons and neutrons in
a nucleus.
Determining p+,n0,e• Protons are always = to atomic number
– Carbon’s atomic number is 6= 6 protons
• Electrons are also = to atomic number
– Unless an ion (+ or – charge)
• Neutrons= atomic mass – atomic number
– Carbon= 12 (at. Mass) – 6 (at.#) = 6
neutrons
IONS
• Ions are charged particles- caused by
having more or less electrons.
• # of protons can never change
• + ions  more protons than electrons
• - ions  more electrons than protons
• Example- Na+2, how many protons and
electrons?
Isotopes
• Different forms of an element due to
varying numbers of neutrons.
– Ex.- Carbon-12, Carbon-13 and Carbon-14
6p/6n
6p/7n
6p/8n
How Elements Combine
A.
Compound
1.
A substance that is made of two or
more different elements bond together.
Example: Salt (NaCl) or Water (H2O)
B.
Molecule
1. A group of atoms held together by
covalent bonds.
Example: Oxygen (O2)
C.
Covalent Bond
1. When two atoms share electrons.
Example:
Water (H2O)
2. Strong bond
3. Found in organic compounds
4. Similar electronegativities
a. Polar Bond
- Occurs when the electrons of a bond are
not shared equally.
- As a result, certain atoms will become
slightly negative while others will become
slightly positive.
Example: Water (H2O)
b. Nonpolar Bond
- Occurs when the electrons of a bond are
shared equally.
Example: Hydrogen Gas (H2)
D.
Ionic Bond
1. When two elements of opposite charge
combine.
2. An ion is an atom that has acquired a positive or
negative charge.
Example: Na+ + Cl- = NaCl
E. Hydrogen Bonds
• Bonds that form between a hydrogen
atom and another atom due to their
high polarity.
• Holds water molecules together.
• weak bond
WATER
A. Importance
1. Provides a place for chemical reactions to occur.
2. Is a means of transport for organisms. (Blood)
3. Makes up a large portion of living organisms. (75-90 %)
B. Hydrogen Bonds
1. Water molecules attract each other.
2. The positively charged H atoms of one water
molecule attract the negatively charged oxygen
atoms of another water molecule.
3. This bond is weak!
4. Hydrogen bonds are important since they help hold many
large molecules, such as proteins, together!
Polarity of H2O
• Water is polar due to the uneven
distribution of charge.
– Oxygen has a stronger pull on e- than
hydrogen so the oxygen side of the molecule
has a slight negative charge.
Properties of Water
• Cohesion- attraction between molecules of
the same substance.
– Due to high polarity of water, can form up to 4
hydrogen bonds.
– Causes water beading and
surface tension.
• Adhesion- attraction between molecules of
different substances.
– Causes meniscus in a graduated cylinder
and capillary action.
Properties of water
• High Specific Heat Capacity- due to the
large number of hydrogen bonds water
can absorb large amounts of heat.
• Evaporative cooling- as water evaporates
it pulls heat from the environment.
– Ex- sweating
• Versatile Solvent- Due to high polarity
water is an excellent solvent.
Solutions
• Solutions are made up of a solute and a
solvent.
• Solute- the substance that is being
dissolved into the solution.
– Ex- iced tea mix
• Solvent- the substance that is dissolving
the solute.
– Ex- Water.
• Water is always the solvent!
VI.
pH (Acids & Bases)
A. pH - Refers to the hydrogen ion (H+) versus hydroxide ion
(OH-) concentration in a solution.
* The pH scale ranges from 0-14.
B. Acid – A substance that has more H+ ions and has
a pH below 7.
*HCl added to water will form H+ and Cl- ions.
C. Base – A substance that has more OH- ions and has
a pH above 7.
*NaOH in water forms Na+ and OH- ions.
pH EXAMPLES:
– Pure water has a pH of 7.0.
(Equal amounts of H+ and OH- ions.)
– Hair remover (Nair) has a pH of 13.0.
– Soda has a pH of 3.0.
Chemical Equations
• C6H12O6 + 6O2  6CO2 + 6H2O + energy
Reactants
Products
• Reactants are combining to form the
products.
• Coefficients- the number that comes
before the element or compound, affects
all elements following.
– Ex- 6CO2 , 6 x C= 6C and 6 x O2= 12 O
Chemical Equations Cont.
• C6H12O6 + 6O2  6CO2 + 6H2O + energy
Reactants
Products
• Subscripts- the number attached to an
individual element, shows the number of
that element.
– Ex O2 , O x 2= 2 oxygen