Chemical Bonding When chemicals form bonds they do so in a way to have the most stable arrangement of their electrons Noble gases are unreactive because they already have a nice, stable arrangement of their atoms

Types of Bonding Ionic bonding: transferring electrons Happens most frequently with atoms from opposite side of periodic table Ionic bonding: transferring electrons Happens most frequently with atoms from opposite side of periodic table Covalent bonding: sharing of electrons Occurs with chemicals that are the same or are near one another on the periodic table Covalent bonding: sharing of electrons Occurs with chemicals that are the same or are near one another on the periodic table

Salts: Composed of ionic solids Composed of ionic solids Strong bonds makes it extremely difficult to melt Strong bonds makes it extremely difficult to melt –NaCl m.p. 801 o C –CaCO 3 m.p. 825 o C  Many dissolve well in water

Solubility Demonstration As a very general rule of thumb As a very general rule of thumb +1 cations and -1 anions are soluble +1 cations and -1 anions are soluble higher charged anions and cations are less soluble higher charged anions and cations are less soluble Predict which of the following will light up brightly with the light bulb apparatus NaBr CuCO 3 LiFCaCO 3

Reactions in Solutions Define solution: ? Define solution: ? Solubility depends on polarity & temperature Solubility depends on polarity & temperature Water is called a universal solvent Water is called a universal solvent What won’t water dissolve? Why? What won’t water dissolve? Why? Like dissolves like Like dissolves like

Sucrose Octane

Solubility and Temperature Solubility of solids in liquids generally increases with increases in temperature Solubility of solids in liquids generally increases with increases in temperature Solubility of gases in liquids generally decreases with increases in temperature Solubility of gases in liquids generally decreases with increases in temperature

Solubility Solubility is also affected by things like acidity (pH) Solubility is also affected by things like acidity (pH) Stalactites and stalagmites form over thousands of years due to the solubility of CaCO 3 in rain water Stalactites and stalagmites form over thousands of years due to the solubility of CaCO 3 in rain water

Acids and Bases Acids are sour, found in citrus foods Acids are sour, found in citrus foods Acids have a pH<7 Acids have a pH<7 Acids produce excess H+ in water Acids produce excess H+ in water Acids donate protons Acids donate protons Acids turn blue litmus red Acids turn blue litmus red Acid + Base  Salt + Water Acid + Base  Salt + Water Bases are bitter Bases are bitter Bases are slippery Bases are slippery Bases are often used in cleaning products Bases are often used in cleaning products Bases have a pH>7 Bases have a pH>7 Bases produce excess OH- in water Bases produce excess OH- in water Bases accept protons Bases accept protons Bases turn red litmus blue Bases turn red litmus blue Neutral substances pH = 7 Neutral substances pH = 7

Acids and Bases continued Acids can be recognized start with H Acids can be recognized start with H Bases usually end with an OH Bases usually end with an OH Strong acids dissociate completely in solution Strong acids dissociate completely in solution HCl + H 2 O  H 3 O + + Cl - Weak acids dissociate a little in solution Acetic acid reaction Acetic acid reaction Strong acids are HCl, HBr, HI, H 2 SO 4, HNO 3, and HClO 4 Strong acids are HCl, HBr, HI, H 2 SO 4, HNO 3, and HClO 4

Acid Base Demonstration Equimolar solutions of HNO3, citric acid, acetic acid, and HCl are here Equimolar solutions of HNO3, citric acid, acetic acid, and HCl are here Which ones will give the brightest light with the lightbulb? Why? Which ones will give the brightest light with the lightbulb? Why?

Bases Strong bases: proton acceptors (bases) that dissociate completely Strong bases: proton acceptors (bases) that dissociate completely Ex. NaOH Ex. NaOH NaOH  Na + + OH - NaOH  Na + + OH - Strong bases are group IA and IIA metal hydroxides All other bases are weak LiOH strong or weak? LiOH strong or weak? NH 4 OH strong or weak? NH 4 OH strong or weak? KOH strong or weak? KOH strong or weak? strong strong CuOH strong or weak? CuOH strong or weak? Weak Weak

pH scale Neutral pH? Neutral pH? Acidic pH? Acidic pH? Basic pH? Basic pH? pH = -log[H+] pH = -log[H+] Log scale therefore pH of 1 is 10x more acidic than a pH of 2 Log scale therefore pH of 1 is 10x more acidic than a pH of 2