[IB Biology Chemistry Unit]
Chapter 2

The Nature of Molecules

ATOMS: fundamental particles of all matter - neutral charge with proton # = electron #.

Protons (+) and neutrons (0) in nucleus

Electrons (-) in orbits around nucleus

Atomic number = number of protons

Atomic mass = mass of protons + neutrons

Subatomic particles seen indirectly via collisions

Charge Neutral atoms: electron # = proton #

Ions: Electrically charged atoms where # of electrons & protons differ (they've gained or lost electrons from/to other atoms).

Atomic Animations:

Atomic Structure

Online Outline of Atoms & Water (McGraw Hill)

Chemical Bonding (Bonding by Analogy: Dog-Bond Bonds)

Ionic vs Covalent Bonding (McGraw Hill)

Ionic Bonds

Chemical Bonds

a. [Ionic bond]: atoms donate or receive electrons from other atoms Example: sodium chloride

b. [Covalent bond]: two atoms share one or more pairs of valence electrons Example: diatomic hydrogen

Most Frequent Elements Found in Organisms

Element Name

% Composition by Body Weight

Importance

Oxygen

65%

a. Used in cellular respiration.

b. Component of water.

c. Component of organic molecules

Carbon

18.5%

a. Backbone of organic molecules

Hydrogen

9.5%

a. Electron carrier.

b. Component of water.

c. Important component of organic molecules.

Other Important Elements Found in Living Organisms

Element Name

Importance of Element

Nitrogen

a. Component of all proteins.

b. Component of all nucleic acids.

Calcium

a. Component of bones & teeth.

b. Muscle contractions.

Phosphorus

a. Component of nucleic acids (DNA).

b. Energy transfers within cells.

Iron

a. Component of blood hemoglobin (carries O2).

Sodium

a. Main positive ion outside cells.

b. Important in nerve impulse transmission.

[Water Notes]

Slichter