Chapter 6 Notes • Ionic Bonds vs Covalent Bonds – Ionic Bonding – Electrons are transferred from one element to another and they bond due to opposite charges. Involve metals bonding to nonmetals. Stronger of the bond types (High melting/Boiling pt) – Covalent Bonding – Atoms do not transfer electrons but share them in order to achieve stability. Follow octet rule (strive for 8 valence electrons except hydrogen which only wants 2). Involve nonmetals bonding to nonmetals. Chapter 6 Notes • Why do atoms/compounds react/bond? – Reactions occur only if an atom or compound will become more stable than it already is. This is why when you mix some substances nothing happens, but others you do get a reaction. Chapter 6 • Repulsive forces vs Attractive forces – Covalent bonds are made up of these two forces that hold the atoms together. – Attractive forces – Opposite charges are attracted to each other. Thus the electrons of one atom are drawn to the nucleus of other atoms making an attractive force. – Repulsive forces – Like charges repel, so as attraction occurs the electrons of the respective atoms get to close and repel each other. This is why they often compare covalent bonds to springs. Chapter 6 • Bond length and energy – Bond length is inversely related to its energy. The longer the bond is the less energy the bond has and the easier it can be broken. The ideal covalent bond has what is called maximum bonding where the attractive forces are exactly equal to the repulsive forces. Chapter 6 • The electronegativity of an atom (when a bonded atom doesn’t equally share electrons with the other atoms) can create compounds that are polar. When one end has a positive charge and the other is more negative. Water is polar because oxygen has a high electronegativity causing it to hog Hydrogens electrons. (+ end and a – end) Chapter 6 • Intermolecular forces – other weak forces acting on covalent bonds – London Forces – weak forces between nonpolar substances. – Dipole forces – when two polar substances are close together the attraction between the positive and negative ends. Closer they are the stronger the force. (Hydrogen bonds – when very close together involving a H) Chapter 6 • Naming Covalent Compounds – We use prefixes to represent the number of atoms involved in the compound: • • • • • • • • • • 1 – Mono 2 – Di 3 – Tri 4 – Tetra 5 – Pent 6 – Hex 7 – Hept 8 –Oct 9 – Non 10 – Dec Chapter 6 • Rules to Naming Covalent Compounds – 1st Simply name the first element. Add the prefix needed if you have more than one of it. – 2nd Add prefix needed (always) then name second element and change ending to ide. Chapter 6 • Lewis Dot Structures (Electron Dot) – Using dots to represent the number of valence electrons in an atom and how they interact in a chemical bond. – Single bonds (one shared pair) – Sigma (one bonding site) – Double Bonds (2 shared pairs) – Sigma bond and a Pi bond (bonds over multiple sites) – Triple bonds (3 shared pairs) Chapter 6 • Diatomic Elements/Molecules – Too reactive by themselves so in order to maintain stability they bond to another of themselves • Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Bromine, and Iodine Chapter 6 • Oxidation Numbers – This is the number of electrons an atom wants to gain or lose to become stable (octet). – Example • H3PO4 – H = +1 – P = +5 – O = -2 Chapter 6 • Structural, Molecular, and Empirical Formulas – Structural Formulas – Drawing of what the molecule looks like including all parts. • Ex. Chapter 6 • Molecular Formulas – The total number of each element in a compound • Ex. C4H10 • Empirical Formula – Simplest whole number ratio of elements » C2H5 Chapter 6 • Polymers – Long chains of molecules • Hydrocarbons – Compounds consisting of primarily Carbon and Hydrogen – Organic Chemistry Chapter 6 • Naming Hydrocarbons – Based on the number of carbons and how those carbons are bonded to each other. Also have special endings for different functional groups attached in the molecule. Chapter 6 • Prefixes for number of carbons – – – – – – – – – – Meth (1 C) Eth (2 C) Prop (3 C) But (4 C) Pent (5) Hex (6) Hept (7) Oct (8) Non (9) Dec (10) • Add the prefix CYCLO to the prefix if the carbons form a ring Chapter 6 • Ending of hydrocarbon name is based on the types of bonds between the Carbons and if functional groups present – All single bonds between C’s no functional groups ending is ANE – If you have a double bond or multiple double bonds and no functional group ending is ENE – If you have a triple bond between the C’s and no functional groups ending is YNE • Hint if the hydrogens are double the carbons +2 you have single bonds • If Hydrogens are double the C you have double • If the Hydrogens are double the C –2 you have a triple bond