Download Biology 105

Chapter 2: Atoms and
Molecules
Pages 26-42
Student Outcomes
Name the principal chemical elements in
living things and their important functions.
Compare and contrast the physical
properties and locations of an atom.
Distinguish among chemical formulas of a
substance.
Student Outcomes
Explain how hydrogen bonds between
adjacent water molecules govern many of the
properties of water.
Distinguish between the terms oxidation and
reduction, relating these processes to the
transfer of energy.
Contrast acids and bases and the pH scale.
Compounds
Inorganic
Organic-carbon based
Common elements of life
Carbon
Hydrogen
Oxygen
Nitrogen
Additional lesser elements (calcium,
potassium, etc) found on page 27
Elements of Earth’s Crust
Top ten of abundance
Oxygen
Silicon
Aluminum
Iron
Calcium
Sodium
Magnesium
Potassium
Titanium
Hydrogen
Elements
Atom - smallest portion of an element
that retains its chemical properties
Electron - negative charge
Proton - in nucleus, positive charge
Neutron - in nucleus, neutral charge
Element Properties
Chemical symbol
C – Carbon
0 – Oxygen
Na-???
Atomic number
Atomic mass
Isotopes
Isotopes
Differ in the number of neutrons, can be
interchangeable
Radioactive decay can be used to
measure age of a sample (1/2 life)
Carbon 14
Electrons
Orbitals
Electron shells and valence shells
Atoms are most stable when valence
shell is filled
Chemical Formulas
Molecule
Compound
Molecular - Water: H20
Structural - Water: H--0--H
Molecular Mass -
Molecular Mass
Find the mass of the following
molecules:
H20
02
C02
CH4
NH3
H2CO3 - (Carbonic acid)
C6H1206
Chemical Equations
Reactants and Products
H20 + CO2 + light -> C6H1206 + 02
Chemical Bonds
Covalent-sharing of electrons to fill
outer shell
Single
Double
Triple
Chemical Bonds
Ionic
Cations and anions
An ionic bond - forms as a result of the
attraction between positive (cation) and
negative (anion) charges
NaCl - Na+ Cl-
Compounds of Ionic bonds can separate
in water (solvent/solute)
Hydrogen Bonds
Bond between Hydrogen and another atom.
Very common and important bond in
organisms
Type of covalent bond
Hydrogen end will inherit a positive charge, the
other end - a negative charge.
These Hydrogen bonds are weak
individually, but strong in large numbers
Electronegativity
Measure of an atom’s attraction for
electrons in chemical bonds
Nonpolar - 02, CH4, H2
Polar – water (one end slightly +, one
slightly-)
Redox Reactions
Oxidation - atom or molecule loses
electrons
Reduction - atom or molecule gains
electrons
Water molecules
Cohesion - attraction of water molecules to
each other
Adhesions - attraction of water molecules to
other molecules
Capillary acton - tendency of water
molecules to move against gravity when in
narrow tubes
Surface tension - water can ‘bulge’ over the
edge
Hydrophillic vs hydrophobic
Makes an excellent solvent (dissolves others)
Water
Calorie (cal) - the heat energy required to
raise the temp. of 1 g of water 1 deg C.
This is known as its specific heat.
Solid form is less dense than liquid form
Water is most dense at 4˙C
pH
• The degree of a solution’s acidity.
• Neutral solution
• Acidic solution-proton donor
• Basic solution-proton acceptor
• Hydrogen(H+) vs hydroxide (OH-) ions
• Buffers help maintain a neutral solution