1. *chemical behavior due to electrons
The Chemical Basis of Life
Energy levels of electrons
*chemical behavior due to electrons
Electron configuration and chemical properties:

2. a pair of shared electrons two pairs of shared electrons
Covalent Bonds
A covalent bond forms when two atoms share one or more pairs of outer-shell electrons.
Atoms held together by covalent bonds form a molecule.
Name
molecular formula
Hydrogen gas H2
Oxygen gas O2
Methane CH4
Electron configuration
Structural formula
Space-filling model
Ball-and-stick model
Single bond
a pair of shared electrons
Double bond
two pairs of shared electrons

3. Sodium chloride (NaCl)
Ionic Bonds
When an atom loses or gains electrons, it becomes electrically charged.
Charged atoms are called ions.
Ionic bonds are formed between oppositely charged ions.
Outer shell
has 1 electron
has 7 electrons
The outer electron is stripped
from sodium and completes
the chlorine atom’s outer shell Na
Sodium atom Cl
Chlorine atom
Complete
outer shells
The attraction
between the
ions—an ionic
bond—holds
them together
Na
Sodium ion
Cl
Chlorine ion
Sodium chloride (NaCl)

4. Hydrogen Bonds
Water is a compound in which the electrons in its covalent bonds are shared unequally.
This causes water to be a polar molecule, one with opposite charges on opposite ends.
slightly 
slightly  H H O
slightly –

5. Hydrogen bonding Weak bonds formed between hydrogen and another atom
Surface tension of water
Important as intramolecular bonds, giving shape to proteins and other biomolecules

6. WATER AND LIFE
Life on Earth began in water and evolved there for 3 billion years.
Modern life remains tied to water.
Your cells are composed of 70%–95% water.

7. Properties of Water
Numerous properties due to the hydrogen bonding

8. Properties of Water Cohesion Adhesion Microscopic tubes
Evaporation from
the leaves
Microscopic tubes
Cohesion due to
hydrogen bonds
between water
molecules
Flow of water
SEM

9. Properties of Water Heat and temperature
Water can absorb and store large amounts of heat while only changing a few degrees in temperature.
Water can moderate temperatures.

10. Properties of Water
Surface tension is the measure of how difficult it is to stretch or break the surface of a liquid.

11. Water is the solvent of life
*solution
*solvent *solute *aqueous solution

12. The Chemical Basis of Life
*hydrophilic
Hydrophilic and hydrophobic substances
*hydrophobic
The dissociation of water molecules
H2O H+ + OH-
*acid
*base
Acids and bases

13. greater H concentration lower H concentration
Acids, Bases and pH
Basic
solution
Neutral
Acidic
Oven cleaner
Household
bleach
Human blood
Pure water
Grapefruit juice,
soft drink
Lemon juice,
gastric juice
Household ammonia
Milk of magnesia
Seawater
Tomato juice
Urine
pH scale 1 2 3 4 5 6 7 8 9 10 11 12 13 14
greater H concentration
Increasingly acidic
lower H concentration
Increasingly basic
[H+]  [OH–]

14. Carbon and Organic Chemistry
Carbon is a versatile atom.
Carbon forms large, complex, and diverse molecules necessary for life’s functions.
Organic compounds are carbon-based molecules.
Structural
formula
Ball-and-stick
model
Space-filling
model

15. Carbon and Organic Chemistry
Variations in Carbon skeletons
Carbon skeletons vary in length
Carbon skeletons may be unbranched or branched
Carbon skeletons may have double bonds,
which can vary in location
Carbon skeletons may be arranged in rings

16. Chemical Components of Cells
*structural isomers
*geometric isomers
*enantiomers
Example of enantiomers:

17. Hydrocarbons Larger hydrocarbons form fuels for engines.
Hydrocarbons of fat molecules fuel our bodies.

18. Carbon and Organic Chemistry
The unique properties of an organic compound depend not only on its carbon skeleton but also on the atoms attached to the skeleton
These atoms are called functional groups
Some common functional groups include:
Hydroxyl group
Carbonyl group
Amino group
Carboxyl group
Found in alcohols
and sugars
Found in amino acids
and urea in urine (from
protein breakdown)
Found in amino acids,
fatty acids, and some
vitamins
Found in sugars