Transcript basic chemistry

CHEMISTRY
The Building Blocks of Biology
Matter
• Anything that has mass and occupies
space.
• Solid, Liquid, Gas
Elements
Biological Elements
•
•
•
•
•
•
96%
Nitrogen
Carbon
Hydrogen
Oxygen
Phosphorous
Sulfur
Elements
• Atom = smallest unit of matter unique to a
particular element.
– (smallest “piece” of an element)
• Molecule = union of 2 or more atoms.
• Compound = union of 2 or more different
atoms.
Atomic Structure
• Determines how atoms act.
• Protons (+)
Nucleus
• Neutrons (no charge)
• Electrons (-)
Orbiting
• Atomic #
• Atomic Mass (Mass #) – an approximation.
Models of Atomic Structure
Cloud of negative
charge (2 electrons)
Electrons
Nucleus
Electron Shells
• 1st Shell holds up to 2e• 2nd Shell holds up to 8e• 3rd Shell holds up to 8e-
Which element is this?
“Normally”
• # Protons = # Neutrons = # Electrons
• BUT, not always…
• Isotopes – Atoms with variable #’s of
Neutrons
– Stable & Unstable
• Ions – Atoms with variable #’s of Electrons
Atoms “like” to do 2 things:
1. Be Balanced.
2. Fill their outer-most shells.
“Valence” Electrons
• Those electrons occupying an atom’s
outer-most shell (its “Valence Shell”)
Formation of Ions
• Oxidation – Departure of an e• Reduction – Gaining of an e-
e-
Bonding
• Linking together atoms to form
molecules…
1.
2.
3.
4.
Covalent Bonding
Ionic Bonding
Hydrogen Bonding
(Peptide Bonding)
Covalent Bonding
•
•
Strong
Sharing of valence electrons
A. Non-Polar Covalent Bonds
EQUAL SHARING
H2
H
H
O2
O
O
Covalent Bonding
•
•
Strong
Sharing of valence electrons
B. Polar Covalent Bonds
UNEQUAL SHARING
H2O
O
H
H
Polar Covalent Bonds
• Water…
Because oxygen (O) is more electronegative than hydrogen (H),
shared electrons are pulled more toward oxygen.
d–
This results in a
partial negative
charge on the
oxygen and a
partial positive
charge on
the hydrogens.
O
d+
H
H
H2O
d+
Ionic Bonding
• Electrons are transferred (not shared)
– Oxidation forms a Cation (+ charged).
– Reduction forms an Anion (- charged).
• Bond results from the attraction between
ions of different charge…
Ionic Bonding
• Attraction between a Cation & an Anion.
1 The lone valence electron of a sodium
2 Each resulting ion has a completed
atom is transferred to join the 7 valence
electrons of a chlorine atom.
valence shell. An ionic bond can form
between the oppositely charged ions.
–
+
Na
Cl
Na
Cl
Sodium atom
(an uncharged
atom)
Chlorine atom
(an uncharged
atom)
Na
Na+
Sodium on
(a cation)
Cl
Cl–
Chloride ion
(an anion)
Sodium chloride (NaCl)
Hydrogen Bonding
• Weak
• A hydrogen atom covalently bonded to one
electronegative atom is also attracted to
another electronegative atom.
—
+
Hydrogen Bonding
H
Water
(H2O)
O
H
d+
d–
Ammonia
(NH3)
N
H
d+
H
H
d+
A hydrogen
bond results
from the
attraction
between the
partial positive
charge on the
hydrogen atom
of water and
the partial
negative charge
on the nitrogen
atom of
ammonia.
Next…Water