Chapter 2
The nature of molecules.
Elemental and molecular composition of living matter:
1. Elemental composition
2. Structure of an atom
3. Chemical bonds.
Elements Common in Living Things
Elemental composition of earth’s crust.
Chemical composition of living
material:
1. Major elements (95%)
O, H, C, N
2. Minor elements (5 %)
Na, K, P, Ca, Mg, Cl, S,
3. Trace elements
EARTH’S CRUST
HUMAN
PUMPKIN
Oxygen
47
Oxygen
65
Oxygen
85
Silicon
28
Carbon
18
Hydrogen
11
Carbon
3
Aluminum
8
Hydrogen
10
Iron
5
Nitrogen
3
Potassium
0
Calcium
4
Calcium
2
Nitrogen
0
Sodium
3
Phosphorus
1
Phosphorus
0
Potassium
3
Potassium
0
Calcium
0
Magnesium
2
Sulfur
0
Magnesium
0
Sodium
0
Iron
0
Chlorine
0
Sodium
0
Structure of an ATOM:
Atom Structure
Structure of the noble gas
NEON
Both the K (2 e-) and L (8 e-)
are completely filled: the
atom is unreactive.
nucleus
electron
neutron
proton
Atom number = # electrons = # protons
Atom mass = # protons + # neutrons
Atom Structure
The ‘octet’ rule: atoms tend to establish
completely full (8 electrons) outer energy levels.
Atoms bond together to form molecules:
Covalent Bonds:
Ionic (bond) Interaction:
Chapter 2
The nature of molecules.
Water is a dipole.
pH and buffers.
Water:
Chemical Bonds:
Single covalent bond
A pair of electrons
is shared equally
in a covalent bond.
Double covalent bond
Water Molecule:
Polar covalent
bond
Water is a dipole:
Water is a DIPOLE
Water forms Hydrogen bonds:
Carbonyl-group
Hydrogen bond
Hydroxyl-group
Water molecules
Butanol and water
Water is COHESIVE:
Water is
COHESIVE
Water vapor
Liquid water
Ice
High specific heat.
Ice is less dense
than water.
Consequence for
life on earth?
Water has high specific heat:
Water has high heat of vaporization:
Water has a high heat of vaporization.
Cooling of a surface by transition from liquid to gas.
Water is ADHESIVE:
Capillary Action
Water dissolves polar molecules:
Spheres of Hydration Around Two
Charged Ions
Salt (NaCl) dissolves in water and separates into Na+ and Cl-
Hydration shell or water mantle
Water ionizes:
Acids and bases:
pH is a measure of (free) [proton]:
Acids and Bases:
Buffers maintain free H+ (pH) though
protons are added or removed:
Buffers maintain free H+ (pH) though
protons are added or removed:
The End.