Ch 6.1 Chemical Bonding Chemical Bonds the attractive forces that hold different atoms or ions together (Intramolecular or electrostatic Forces
Why Bond? Atoms bond to achieve a full outer energy level OCTET RULE: They want 2/8 VALENCE electrons. Few exceptions Ex. BF 3 and SF 6
I guess not everyone can hold 8 e-
Bond Structures Ionic Crystal or formula Units (strongest Bond) Network Structures (Strong Covalent solids) Molecular (most common covalent bond, weakest)
Chemical Bonds: Types COVALENT METALIC IONIC ALL NONMETALS atoms METAL and NONMETAL ions Holding a compound or Holding a compound ALL METALS element together together holding an element together
Ch. 6.4 Metallic bond Formed by the attraction between positively charged metal ions and the sea of electrons around them. Held together by delocalized, free-flowing electrons along the bond Holds metal elements and alloys together
Metallic bond Properties Strong Bonds Malleable High melting points Ductile Good conductors of electricity
Ch 6.1 Electronegativity Difference (END) the difference in electronegativity between two atoms in a bond. Bonds are rarely ionic or covalent.
Electronegativity Difference (ED) EX. NO N=3.0 O=3.4 [3.4-3.0] = 0.4 Electronegativity difference of NO = 0.4 Tells us two things
Bond Properties and Polarity If ED is > 1.7, then the compound has more polar ionic properties. (strongest) If ED is < 1.7, then the compound has more polar covalent properties If the ED is < 0.3, then the compound is nonpolar covalent. (weakest)
Polarity (ch. 6.1, 6.5) Property of a molecule s bond caused by an unsymmetrical charge distribution Polar molecules are unsymmetrical in shape Nonpolar molecules are symmetrical in shape It is important to note that nonpolar molecules can have polar bonds
Polar Covalent Molecules The atom with the higher electronegativity will attract the electrons more strongly. This will cause partial charges to develop on (-ع +ع) each side of the molecule Contain Dipole forces Unequal Sharing
Unsymmetrical Shape Polar molecule
Unequal Sharing
Nonpolar Covalent Molecules Molecules where the atoms have similar electronegativity's This will cause partial charges cancel Equal sharing Held by weaker London dispersion forces
+ Boron Trihydride Polar bond B + + Same all around Symmetrical shape Nonpolar molecule
Equal Sharing
Using Dot Diagrams Dot diagrams may be used to show how electrons are shared or how they will be transferred
Ch 6.2 Covalent Bonds A bond formed by the sharing of valence electrons (co VALENT) Also called molecules Formed between two or more nonmetal atoms
TYPES OF BONDS SINGLE BONDS DOUBLE BONDS TRIPLE BONDS
Molecular bond Properties (<1.7) Weak bonds (molecules) The longer the bond the less bond energy needed to break bond Molecular compounds have low melting points and are bad conductors of electricity (no ions) Can be solids, liquid or gas phase at room temp.
Dot Diagrams and Structural Formulas
VSEPR and Molecular Geometry
Ch. 7.1 Molecular Formula The actual formula of a covalent molecule.
Empirical Formula The simplest whole-number ratio a chemical formula can have. Different covalent compounds can have the same empirical formula Ionic formulas are always empirical
Organic Molecules
Naming Covalent Compounds Prefixes for # of atoms 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. H 2 O two H atoms
Naming Covalent Compounds Step 2 Identify the number of atoms in the 2 nd element. Ex. H 2 O one O atom
Naming Covalent Compounds Step 3 Name the compound with the appropriate prefixes. Ex. H O 2 dihydrogen monoxygen
Naming Covalent Compounds Step 4 add an -ide ending to the second element Ex. Dihydrogen monoxide
Ionic bond (ch. 6.3) A bond formed by the attraction between oppositely charge ions. The transferring of valence electrons Each ion will have 2/8 valence electrons Formed between metal ions and nonmetal ions Na + + Cl - NaCl
Ionic bond Properties (>1.6) Very Strong bonds (formula units) Compounds made up of ionic bonds have high melting points and are good conductors of electricity when dissolved or melted (ions free to move) solid phase (salts)
Ch. 7.1 Writing Ionic formulas Step 1 Calcium Fluoride Write both positive and negative ions (use ion table if you need it) Ca 2+ F -1
Writing Ionic Compounds Step 2 Criss-cross numbers down, making subscripts Ca 2+ F -1 Ca 1 F 2
Writing Ionic Compounds Step 3 Combine your new compound. Ca 1 F 2 Ca 1 F 2
Ionic bonds Ionic bonds may contain polyatomic ions in them. An ion made from two or more atoms covalently bonded together that act like a single ion. A molecule with a charge, example sulfate (SO 4 ) -2 EX Na +1 + (SO 4 ) -2 Na 2 (SO 4 ) Covalent Bond Ionic bond between 2 ions
Polyatomic ion Aluminum Carbonate Al +3 (CO 3 ) -2 Al 2 (CO 3 ) 3 Al 2 (CO 3 ) 3
Ch. 7.1 Naming Ionic Compounds Step one Name the first ion in the formula Ex. CaCl calcium 2 Na (SO ) - sodium 2 4
Naming Ionic Compounds Step two Name the second ion Ex. CaCl Calcium Chloride 2 Na (SO )-sodium sulfate 2 4
PROBLEM-Group B Ex. Fe 2 O 3 and FeO are different compounds Fe 3+ O 2- = Fe 2 O 3 Fe 2+ O 2- = FeO
Solution-Roman Numerals Same naming scheme Add a Roman Numeral to identify the charge of the metal.
Solution-Roman Numerals Fe 3+ O 2- = Fe 2 O 3 Fe 2+ O 2- = FeO Fe 2 O 3 = iron(iii)oxide FeO = iron(ii)oxide
BONDING REVIEW-