Transcript Basic Chemistry - Ashley Grapes Biology Education

Basic Chemistry
Objectives for Today
• Importance of Chemistry
• Matter
• Atoms
• Isotopes/Carbon dating
• Ions
• Valence electrons
Importance of Chemistry
• Known as the ‘central science’
• Chemistry is the basis of biology
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Matter is made from atoms
Molecules
Water
pH
Matter
• Everything is made up of matter (if it’s not
matter, it’s energy)
• Matter is anything that has mass and takes up
space
• All matter is composed of atoms, the smallest
basic unit
• What’s the difference between an atom and
an element?
• How many different kinds of atoms are there?
Answers
Structure of an Atom
• Protons
• Positively charged particle in nucleus
• Determines identity (atomic #) of an atom
• 1 protons weighs 1 amu (atomic mass unit)
• Neutrons
• Neutrally charged particle in nucleus
• Isotope: when atom has same # of protons but dif # of neutrons
• 1 neutron weighs 1 amu
• Electrons
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Negatively charged particle flying around the outside of nucleus
Gives atoms their chemical properties
Mass is negligible
Ion: when the number of protons and electrons differs
Isotopes
Concept Check
Assume this lithium atom is neutral
• How many protons does it have?
• How many electrons does it have?
• How many neutrons does it have?
Carbon Dating with Carbon-14
Half-life: time it takes for 1/2
of the atoms to decay; can be
used to determine age of
biological material.
The Periodic Table for Life
CHNOPS!
Element of life
• CARBON!
• Organic Chemistry = chemistry of life = carbon
chemistry
• The Octet Rule: atoms want eight electrons in
their outer shell
• Carbon is the smallest (most flexible) atom on
the PT with exactly half that number (4 e-) so
it is very unhappy and want to form bonds
Valence Electrons
• The electrons in the outermost shell
• The key player in chemical properties/bonding/molecule formation
because of the Octet Rule
• Atoms will combine is a way where all atoms are ‘happy’ with a full
outer shell
Ions
• Group 8 are the noble gases don’t bond with
anything; inert gases; neutral SNOBS!
• Group 1 want to lose one e- and become 1+
• Group 7 want to gain one e- and become 1• Cation: a positively charged ion
• Anion: a negatively charged ion
Importance of Ions in Biology
• Chemical bonding
• Structure of proteins
• Membrane potential
• pH
• Muscle contraction
• Neuron signaling
• Enzyme catalysis
2. Which drawing depicts the electron configuration of neon
(2010Ne)?
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A
B
C
D
E
3. Which drawing depicts an atom with a valence of 2?
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A
B
C
D
E
4. Based on electron configuration, which of these elements
would exhibit chemical behavior most like that of oxygen?
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S
P
H
C
N
5.Nitrogen (N) is much more electronegative than hydrogen
(H). Which of the following statements is correct about the
atoms in ammonia (NH3)?
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The nitrogen atom has a partial positive charge.
Each hydrogen atom has a slight negative charge.
There are covalent bonds between the hydrogen atoms.
The nitrogen atom has a strong positive charge.
Each hydrogen atom has a partial positive charge.
6.The atomic number of sulfur is 16. Sulfur combines with
hydrogen by covalent bonding to form a compound,
hydrogen sulfide. Based on the electron configuration of
sulfur, we can predict that the molecular formula of the
compound will be
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HS
HS2
H2S
H3S2
H4S
Basic Chemistry
Part II
Today’s objectives
• Chemical bonds
• Nonpolar vs. polar
• Molecule formation
• Oxidation/Reduction
• Reaction Rate
• Some important molecules in biology
Question
• Does most matter exist as pure elements?
• NO! because unless you’re a noble gas, you are unstable and want to
form bonds in order to fill your outer shell
Types of Bonds
• Covalent Bond: the strongest type of bond where electrons are
shared sharing of
• Polar covalent: electrons shared unequally
• Non-polar covalent: electrons shared unequally
• Ionic Bond: electrons transferred between atoms, making ions that
are subsequently attracted to each other
• Hydrogen Bond: bond between two molecules resulting from an
electrostatic attraction between a proton in one molecule and an
electronegative atom in the other.
• Electronegative: larger atom that pulls electrons towards itself
Types of Bonds
Ions & Oxidation Number
• Oxidation #: The charge an atom has after gaining or losing electrons
in order to fill its outer shell
Finding Oxidation #
• Unless otherwise stated, most molecules are neutral
Molecules vs. Compounds
• Molecule: two or more atoms
bonded together
• Diatomic element: a molecule that
contains two atoms of the same
element
• Hydrogen gas and oxygen gas always in
diatomic form
• Compound: two or more elements
bonded together
Lewis Dot Structures
• Only show valence electrons
• You are able to see how many electrons are needed to fell outer shell
and can predict what the molecules will look like
You try:
CO2
Oxidation/Reduction Reaction (Redox)
• Oxidation: loss of an electron
• Reduction: gain of electron
Reaction Rate
• Question: Do you think most reaction
happen spontaneously?
• Anything that will cause molecules to
bombard each other will increase a reaction
• Stirring
• Increase temperature (temp is a measure of
kinetic energy not heat!)
• Increasing concentration
• Decreasing volume of solution
• Catalyst: a substance/molecule that increases
rxn rate by decreasing the activation energy (AE)
• AE: energy required to start a chemical reaction
Biochemistry – “the chemistry of life’
• the branch of science concerned with the chemical and
physicochemical processes that occur within living organisms.