Compounds & Molecules Compounds - made of 2 or more elements and are chemically combined Chemical bond - force that holds atoms together Formulas - represent compounds, made up of subscripts and symbols

Compounds and Mixtures Differ Mixtures are made of different substances that are physically placed together. Compounds are made of different atoms that are chemically bonded together. The substances in mixtures may exist in any amount. The atoms in compounds are in definite proportions.

Mixtures do not have a chemical formula. Compounds do have a chemical formula. The substances in mixtures keep their individual properties. The atoms in compounds lose their

Examples of compounds Water H2O Salt (sodium chloride) NaCl Table sugar C12H22O11

Compounds are always made of the same elements in the same proportions H2O is water (2H:1O) H2O2 is hydrogen peroxide (1H:1O)

2 Types of Formulas Molecular - H2O gives the number and kinds of atoms Structural - shows how the atoms are bonded

Chemical structure affects the properties Quartz (found in rocks) and Table salt - exist as a large network of bonded atoms Sugar and water - made of many separate molecules

Quartz - forms crystals - bond is very strong - hard and inflexible solid - high melting and boiling pt. Sugar - forms molecules - weaker bonds - low melting and boiling pt.

Review Questions: What does a formula represent? What two things is a formula made of? What are chemical bonds? In this formula: C8H16O8, what is the ratio of Carbon to Hydrogen? 4. In the above formula, how many total atoms are there? 5. Name the two types of formulas. Which type shows how the atoms bond?

Is the formula for water always H2O? Are the atoms in a compound always in the same proportion? 7. Make a T-chart to show 3 differences between quartz and table sugar. 8. Define compound. 9. Make a T-chart to show 4 differences between mixtures and compounds.

TYPES OF BONDING Ionic - formed between oppositely charged ions - involves a transfer of electrons - formed between a metal and a nonmetal - Na+ Cl- NaCl - form crystals

Covalent - sharing of electrons - occurs between 2 nonmetals - C + O ------> CO (carbon monoxide) - form molecules

Polyatomic ions - group of atoms that act as a single unit Examples: Phosphate PO43- Carbonate CO32- http://www.chemistry.wustl.edu/~edudev/LabTutorials/PeriodicProperties/Ions/ions.html#Index

Review Questions: For Questions 1 - 7 write Ionic or covalent, depending on which is being described. Involves a sharing of electrons Involves a transfer of electrons Forms molecules Forms crystals Formed between a (+) and a (-)ion Between 2 nonmetals Between a metal and a nonmetal

For questions 8 - 10, tell if the following compounds have been formed by ionic or covalent bonds. MgCl2 9.CO 10.ZnF2

NAMING COMPOUNDS Ionic compounds metal listed first, nonmetal second NaCl sodium chloride (change second element letters to “ide”) Name these: NaF, CaCl2, HI

Writing Ionic Formulas Give the formula for aluminum fluoride Al charge is 3+ F charge is 1- Have to balance to zero Al is 3+ so need to make F 3- F is 1- x 3 = 3 F’s AlF3

Give the formula for calcium chloride Ca charge is 2+ Cl charge is 1- (take times 2) CaCl2 Give the formula for sodium oxide _____? Sodium Oxide: Na2O

Write formulas for ionic compounds made between these atoms: Li and O 5. Be and Cl Ca and O 6. Mg and S Al and O 7. Na and S Mg and Br 8. Al and N

Naming Covalent Compounds -prefixes are used to name compounds with 2 elements CO2 carbon dioxide N2O4 dinitrogen tetraoxide Before showing water as dihydrogen monoxide do the activity handout about water as an article review opinion.

Try these BI3 NaN3 SiO2 Boron Triiodide; Sodium trinitride; Silicon dioxide; Dihydrogen monoxide (water)- removed so can do the article review

-compounds that contain carbon Examples of carbon compounds Organic Compounds -compounds that contain carbon Examples of carbon compounds hydrocarbons- contain only C and H methane CH4, butane C4H10 http://www.nyu.edu/pages/mathmol/library/hydrocarbons/ alcohols - C, H, and O isopropyl alcohol C3H8O This is for introduction, we will look at reactions and polymers later (in Q3 beginning) and in the lab.

Many organic compounds are POLYMERS Large molecules made of a repeating unit Natural polymers - rubber, wood, cotton, wool, protein, DNA Man-made polymers - plastics, fibers like rayon, nylon

Biochemical compounds are organic Examples: Carbohydrates - sugars Proteins - made of amino acids Lipids - fats and oils DNA - genetic material