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CHAPTER 2

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ELEMENTS: Periodic Table

____ total elements : ____ natural and ____ man-made

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ORGANIZATION OF PERIODIC TABLE

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ATOMIC STRUCTURE

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THE NUCLEUS OF AN ATOM

How does an atom stay together?

ELECTRON ENERGY LEVELS

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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

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ISOTOPES

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CHEMICAL BONDING

Bonding

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+ =

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!

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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.

IONIC BOND:Bohr Method

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IONIC BOND:Lewis Dot Structure

NaCl

MgO

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.

REDOX REACTIONSReduction = gain electronsOxidation = lose electrons

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COVALENT BOND:Bohr ModelBohr Model Method:

Step 1: Draw the energylevels for each element separately.

Step 2: Show the energy levels joined (similar to the top picture)

All diatomic elementsDemonstrate a Covalent bondRemember: BrINClHOF(Chlorine isshown to the right)

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Mo

lecular fo

rmu

laCOVALENT BOND:Lewis Dot Structure

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)

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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

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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

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CHEMICAL EQUATIONS

Reactant

Reactant

Reactant

Reactant

Product

Product Product Product

Product

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CHEMICAL REACTIONSEndothermic vs. Exothermic

Exothermic– energy released – reactants have more energy than products

Endothermic – energy absorbed – products have

more energy than reactants

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SECTION 3WATER AND SOLUTONS

bRONZE

brass

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3 unique

characteristics of water

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POLARITYOF

WATER

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HYDROGEN BONDING(Weak Bond)

Surface Tension is caused by…

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COHESION / ADHESION / CAPILLARITYCohesion 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

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SOLUTIONS

bRONZE

brass

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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.

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ACIDS / BASESAcidity / Alkalinity depends on the amount of hydronium

atoms.

HCl + NaOH        NaCl + H2O

(Acid) (Base)---(Salt) (Water)

If more hydroxide than hydrogen= BASE

If hydrogen= hydroxide =

NEUTRAL

If more hydrogen than hydroxide = ACID

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TESTING FOR ACIDS / BASES