Compounds and Molecules 4.1 vid

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 Formula C12H22O11 can only be sugar H20 can only be water

Parts to the Formulas 2H2O Subscript Coefficient

Parts to the Formulas Coefficient – gives the amount of molecules or moles Subscript – tells the number of atoms or ions

Chemical Structure Bond length -the distance between two bonded atoms Bond angle -the angle formed between two bonded atoms

-atoms are represented balls, bonds are represented by sticks. Models of compounds Ball and stick model -atoms are represented balls, bonds are represented by sticks. H H Bond Angle O Bond length

-chemical symbols represent the atoms. Models of compounds Structural formulas -chemical symbols represent the atoms. H H O

-show the space occupied by each atom represented in the compound. 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 Na+ + Cl- NaCl A bond formed by the attraction between oppositely charge ions. The joining of a positive metal ion and a negative nonmetal ion Na+ + Cl- NaCl

Ionic bond NaCl Na+ + Cl- Formed by transferring electrons Now each ion will have 8 valence electrons NaCl Na+ + Cl-

Ionic bond Properties They form network structures high melting points Good 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 Formulas Calcium Fluoride Step 1 - Look up both positive and negative ions Ca2+ F-1

Writing Ionic Compounds Step 2 Criss-cross numbers down, making subscripts Ca2+ F-1 Ca1 F2

Writing Ionic Compounds Step 3 Combine your new compound. Ca1 + F2  Ca1F2

Polyatomic ion Aluminum Carbonate Al+3 (CO3)-2 Al2 (CO3)3 Al2(CO3)3

Naming Ionic Compounds Step one – Name the first ion in the formula Ex. CaCl2 – calcium Na2(SO4) - sodium

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

PROBLEM Fe3+ O2- = Fe2O3 Fe2+ O2- = FeO Ex. Fe2O3 and FeO are different compounds from different ions Fe3+ O2- = Fe2O3 Fe2+ O2- = FeO

Solution-Roman Numerals Same naming scheme Add a Roman Numeral to identify the charge of the metal ion.

Solution-Roman Numerals Fe2O3 = iron(III)Oxide FeO = iron(II)Oxide Remember!!! 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 – 6 Hepta - 7 Octa - 8 Nona - 9 Deca - 10

Naming Covalent Compounds Step 1 Identify the number of atoms in the first element Ex. H2O two H atoms

Naming Covalent Compounds Step 2 Identify the number of atoms in the 2nd element. Ex. H2O one O atom

Naming Covalent Compounds Step 3 Name 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 Formula The simplest chemical formula of a compound. Different covalent compounds can have same empirical formula

Ch. 4.4