Compounds and Molecules

4.1vid

What are compounds?

Two or more elements chemically combined to form new substances.

What are compounds?

Chemical Bonds – the attractive forces that hold different atoms or ions together

Bonds distinguish compounds from mixtures.

Chemical FormulaC12H22O11 can only be sugar

H20 can only be water

Parts to the Formulas

2H2O

Coefficient Subscript

Parts to the Formulas

Coefficient – gives the amount of molecules or moles

Subscript – tells the number of atoms or ions

Chemical StructureBond length

-the distance between two bonded atoms

Bond angle-the angle formed between two bonded atoms

Models of compounds

Ball and stick model-atoms are represented balls, bonds are represented by sticks.

O

H H

Bond length

Bond Angle

Models of compounds

Structural formulas-chemical symbols represent the atoms.

H HO

Models of compounds

Space-filling-show the space occupied by each atom represented in the compound. Hydrogen

Oxygen

Structure of Compounds Network Structures = strong solids

Molecules= weak solids, liquids, or gases

Ionic and Covalent Bonding

4.2

fun

Why Bond?Atoms bond so they can become stable!

They want to achieve a full outer energy level

They want 8 electrons.

1. Ionic bond

A bond formed by the attraction between oppositely charge ions.

The joining of a positive metal ion and a negative nonmetal ionNa+ + Cl- NaCl

Ionic bond Formed by transferring electrons

Now each ion will have 8 valence electrons

Na+ + Cl- NaCl

Ionic bond PropertiesThey form network structureshigh melting pointsGood conductors of electricity when dissolved or melted because of their ions

Metallic bond

Formed by the attraction between positively charged metal ions and the electrons around them.

Metallic bond

Held together by free flowing electrons

Hold metallic elements together

Covalent Bonds

Formed when atoms share one or more valence electrons

Formed between non-metals

May form single, double, or triple bonds

Covalent Properties

They are poor conductors of electricity (no ions)

Low melting points.form molecules

Polyatomic ion An ion made of two or more atoms

that are covalently bonded and that act like a single ion.

A molecule with a charge Examples: carbonate (CO3)-2

Nitrate (NO3)-1

Fun

Compound Names and Formulas

4.3

REMEMBER!!!!!!!! If it starts with metal it is an ionic

compound If it starts with a nonmetal it is a covalent

compound If the formula contains a parentheses

(polyatomic ion) it contains both ionic and covalent bonds

If it is just a metal it is metallic

Writing Ionic FormulasCalcium Fluoride Step 1 - Look up both positive and negative ions

Ca2+ F-1

Writing Ionic CompoundsStep 2Criss-cross numbers down, making subscripts

Ca2+ F-1

Ca1 F2

Writing Ionic Compounds

Step 3Combine your new compound.

Ca1 + F2 Ca1F2

Polyatomic ion

Al+3 (CO3)-2

Al2 (CO3)3

Al2(CO3)3

Aluminum Carbonate

Naming Ionic Compounds

Step one – Name the first ion in the formulaEx. CaCl2 – calcium

Na2(SO4) - sodium

Naming Ionic Compounds

Step two – Name the second ion Ex. CaCl2 –Calcium Chloride Na2(SO4)-sodium sulfate

PROBLEMEx. Fe2O3 and FeO are different compounds from different ions

Fe3+ O2- = Fe2O3

Fe2+ O2- = FeO

Solution-Roman Numerals

Same naming schemeAdd a Roman Numeral to

identify the charge of the metal ion.

Solution-Roman Numerals Fe2O3 = iron(III)Oxide

FeO = iron(II)OxideRemember!!!

R.N. is the charge, not the subscript of the metal.

Naming Covalent Compounds

Mono – 1 Di - 2 Tri - 3 Tetra - 4 Penta - 5

Hexa – 6Hepta - 7Octa - 8Nona - 9Deca - 10

Naming Covalent Compounds

Step 1Identify the number of atoms in the first elementEx. H2O two H atoms

Naming Covalent Compounds

Step 2Identify the number of atoms in the 2nd element.

Ex. H2O one O atom

Naming Covalent Compounds

Step 3Name the compound with the appropriate prefixes. Ex. H2O

dihydrogen monoxygen

Naming Covalent Compounds

Step 4 add an -ide ending to the second element

Ex. Dihydrogen monoxide

Empirical FormulaThe simplest chemical formula

of a compound.Different covalent compounds

can have same empirical formula

Ch. 4.4