Pure Substances. What are ions??? IONS – Atoms with a charge! What determines how many electrons...

Pure SubstancesPure

Substances

ElementsCompounds

Ionic Covalent

Polar Non polar

Metalloiods

Metals Nonmetals

What are ions???

IONS – Atoms with a charge!

What determines how many electrons the ion has?

Forming Ions– Octet Rule (rule of 8’s)

• Elements with 5 or more valence electrons will take – GAIN electrons from others to get to 8

• Which groups are these?

• Elements with 3 or less valence electrons will give up –LOSE electrons so they can be stable

Octet Rule (continued)• Elements with 4 valence share their electrons.

These elements form covalent compounds.Draw a line:

ALMOST All Elements want to have a full electrons in valence shell….to be STABLE

They will react with others to get there Exception: He and H only need 2 to feel happy

Octet Rule (continued)

• CATIONS – positively charged atoms, they have LOST electrons

• ANIONS – negatively charged atoms, they have GAINED electrons

• Let’s see how it happens….• http://www.youtube.com/watch?v=lODqdhx

DtHM

Forming Ions Element Valence

e-Lose, gain, or share e-

New Total electrons

Charge of ion

Calcium

Silicon

Bromine

Forming IonsElement Valence

e-Lose, gain, or share e-

New Total electrons

Charge of ion

Li

O

P

Forming IonsElement Valence

e-Lose, gain, or share e-

New Total electrons

Charge of ion

Ga

Kr

Ba

Compare/Contrast Ions and Isotopes

Pure Substances- COMPOUNDS

• What is a compound? 2 or more elements chemically bound together

• Ionic compounds (attraction between opposite charges)– Strong Bonds– Compounds have at least 1 metal

• Covalent compounds– Weak Bonds– Compounds made of nonmetals and/or metalloids

only. NO METALS.

Ionic or Covalent?

•MgBr2

•SiO4

•CO2

•CoF

•H2O

•NaCl

Ionic or Covalent?Water? Alcohol? Melting

pointConduct electricity?

Sodium Chloride

Y N High Y

Sugar Y N Low N

Salicylic Acid

N Y Low N

Sodium Carbonate

Y N High Y

Ionic Compounds

• Ionic compounds– Formed from the

attraction between cations and anions. (Like a north and south pole of a magnet)

– Water molecules can pull ionic compounds apart because the water molecule is polar. (Like a magnet)

– Become electrolytes in H2O

Ionic Compounds

Dissolving Ionic Compounds

• Watch this demonstration

Ionic Compounds

• Why didn’t alcohol dissolve the ionic compounds?

• Once ionic compounds dissociate, electricity passes easily through the solution. Why?

• How are ions formed?

Naming Ionic Compounds

• The cation always comes first in the compound’s formula and name.– For binary compounds, the cation’s name is

unchanged, but the anion’s name has “-ide” added to the end.

• Ex: Aluminum Fluoride, Barium Oxide

– For compounds with polyatomic ions, the polyatomic’s name is unchanged, no matter what. All other rules apply.

• Ex: Calcium Nitrate, Ammonium Chloride

Writing Ionic Formulas

• The subscripts represent the number of ions needed to make a stable compound. (The compound should be neutral overall.)– Ex: Aluminum Fluoride

• Al3+ and F-…..It takes 3 F- to match w/ one Al3+

• AlF3

– Ex: Calcium Nitrate• Ca2+ and NO3

-..It takes 2 NO3- to match w/ Ca2+

• Ca(NO3)2

Polyatomic Ions

• What does the prefix “poly” mean?

• What is an ion?

• Examples– Nitrate= NO3

-

– Phosphate = PO43-

– Ammonium = NH4+

• Don’t make any changes to the subscript of the polyatomic ion.

Covalent Compounds

• Covalent bonds are formed by atoms sharing their valence electrons.

• The shape of covalent compounds determines if they’re polar or non polar

Covalent Compounds

• Like dissolves like– Water dissolves polar covalent compounds

(such as sugar) because water IS a polar covalent compound

– What type of compound is alcohol?• Which compound dissolved in alcohol?• What type of compound was this substance?

• Covalent compounds don’t have charged atoms, so they don’t conduct electricity.

Covalent Compounds

• Octet Rule still applies!– Only exception is Hydrogen…it only needs 2

valence electrons to be stable.

• Lewis Dot diagrams for compounds– Hydrogen Bromide– Silicon Tetrafluoride– Nitrogen Trichloride

Potassium Nitrate

0o C 13.9g

20o C 31.6g

60o C 109g

100o C 245g

Potassium Chloride

0o C 28.0g

20o C 34.0g

60o C 45.8g

100o C 56.3g

Barium Hydroxide

0o C 1.67g

20o C 3.89g

60o C 20.94g

100o C 101.4g

Copper Sulfate

0o C 23.1g

20o C 32.0g

60o C 61.8g

100o C 114g

Warm Up

1. Parts of this mixture separate when allowed to sit for a while.

2. Jewelry and air are examples of this type of mixture.

3. This mixture acts like a solution, but light can be seen as it passes through.

When making Kool-Aid

• What’s the solute?

• What’s the solvent?

• What are three ways to get more of the SOLUTE to dissolve?

Ionic or Covalent?

• CO

• Ca3(PO4)2

• Li2O

• CCl4• AlBr3

Warm Up

• For projectiles (on Earth) that have no initial vertical velocity, what is the only factor that affects how long it takes to hit the ground?

Warm Up

• Give the oxidation number (charge) for each of the following elements when they become ions.

– Ex: Sodium = +1

• Chlorine

• Aluminum

• Oxygen

• Phosphorus

• Strontium

• Francium