CHAPTER 2

ELEMENTS: Periodic Table ____ total elements : ____ natural and ____ man-made

ORGANIZATION OF PERIODIC TABLE

ATOMIC STRUCTURE

How does an atom stay together? THE NUCLEUS OF AN ATOM How does an atom stay together?

ELECTRON ENERGY LEVELS

DIATOMIC ELEMENTS Elements that must exist naturally as 2 atoms bonded together (until it forms a chemical bond with any other element) Br I N Cl H O F H2 N2 O2 F2 Cl2 Br2 I2

ISOTOPES

CHEMICAL BONDING

Bonding Sodium is a silver-colored metal that reacts so violently with water that flames are produced when sodium gets wet. Chlorine is a greenish-colored gas that is so poisonous that it was used as a weapon in World War I. When chemically bonded together, these two dangerous substances form sodium chloride, a compound so safe that we eat it every day - common table salt! = +

IONIC BOND: Bohr Method Bohr Model Method: Step 1: Draw the energy levels for each element Step 2: Show the arrow of transfer. There should be an arrow showing transfer for EACH electron given away. (Just like the top picture) Step 3: State the ions below each atomic structure to indicate that electrons have been gained or lost.

NaCl MgO IONIC BOND: Lewis Dot Structure Lewis Dot Method: Step 1: Write the symbol for each atom separately and show valence electrons (evenly spread out ) Step 2: No arrows. Write ions once transfer has taken place. Show electrons for the ORIGINAL outer shell (the one that gained will show electrons). Remember that ions are written as symbol with superscript. NaCl MgO

REDOX REACTIONS Reduction = gain electrons Oxidation = lose electrons

COVALENT BOND: Bohr Model Bohr Model Method: Step 1: Draw the energy levels for each element separately. Step 2: Show the energy levels joined (similar to the top picture) All diatomic elements Demonstrate a Covalent bond Remember: BrINClHOF (Chlorine is shown to the right)

COVALENT BOND: Lewis Dot Structure Molecular formula Lewis Dot: Step 1: Draw the dot diagram for each element individually (use X and • for different atoms) Step 2: Draw the dot diagram for the compound Step 3: Show the molecular formula (including lone electrons) Molecular formula

STATES OF MATTER Solid Liquid Gas Definite shape Shape of container No definite shape Definite volume Volume of container No def. volume Tightly packed May overlap Very spread out Vibrate in place Move faster Very fast

CHANGES IN STATE 2 types of Latent Heat = energy absorbed (stored) or released Heat of fusion = energy released; Gas to Liquid to Solid Heat of Vaporization = energy absorbed; Solid to Liquid to Gas

CHEMICAL EQUATIONS Reactant Reactant Product Product Reactant Reactant 20

CHEMICAL REACTIONS Endothermic vs. Exothermic Endothermic – energy absorbed – products have more energy than reactants Exothermic– energy released – reactants have more energy than products

SECTION 3 WATER AND SOLUTONS brass bRONZE

3 unique characteristics of water

POLARITY OF WATER

HYDROGEN BONDING (Weak Bond)

Surface Tension is caused by…

COHESION / ADHESION / CAPILLARITY Cohesion attracts molecules of the same kind (water to water) Adhesion attracts molecules of different kinds (tape and hair) Capillarity is the attraction of molecules allowing a liquid to rise

SOLUTIONS brass bRONZE

THE DISSOCIATION OF WATER Step 1: One water molecule bumps into another water molecule Step 2: One of the water molecules dissociates (comes apart). When water dissociates, hydroxide ions (OH-) and a hydrogen ion (H+) are produced.

(Acid) (Base)---(Salt) (Water) If more hydroxide than hydrogen= BASE ACIDS / BASES Acidity / Alkalinity depends on the amount of hydronium atoms. HCl + NaOH        NaCl + H2O (Acid) (Base)---(Salt) (Water) If hydrogen= hydroxide = NEUTRAL If more hydrogen than hydroxide = ACID If more hydroxide than hydrogen= BASE

TESTING FOR ACIDS / BASES