Review of Atomic Model You should be able to: Name and write formula for most chemical compounds Write, balance and predict products for most chemical equations

Anything that has mass and takes up space, or volume. Matter: Anything that has mass and takes up space, or volume. Na NaCl NaCl + H2O NaCl + Pepper

Elements are pure substances containing one type of atom – found on the Periodic Table. The atom is the smallest part that retains all the properties of that element. protons (p+) neutrons (no) electrons (e-) Charge Mass Location +1.6 x 10-19 C -1.6 x 10-19 C 1.67 x 10-24 g 9.11 x 10-28 g Nucleus Orbit clouds

A “staircase” on every Periodic Table separates the metals from the non-metals (with metalloids in between)

Can be qualitative or quantitative Physical properties Testing or measuring these traits will NOT change the original composition (what it is made of) Can be qualitative or quantitative quality quantity State/phase – solid, liquid or gas (at room temperature) Hardness – how easy it is to scratch or dent Viscosity – how easy it flows Melting point – unique temperature needed to change from solid into liquid Boiling point – unique temperature needed to change from liquid into gas

Other examples of Physical Properties: Lustre – shiny (opposite – dull) Malleability – how easy to bend or flatten (opposite – brittle) Ductility – how easy to pull into a wire Solubility – how well it dissolves in water Conductivity – how well it transfers heat/electricity Quantitative traits require a measurement – melting point Qualitative traits don’t need one – state

Trait describes if substance reacts chemically Chemical properties Trait describes if substance reacts chemically Testing or measuring these traits WILL change the original composition (will create something new) Reactivity – does it react quickly? Combustibility – does it ignite or burn? Corrosion – does it react with acids? Oxidation – does it react with air? Toxicity – does it react with the body? Testing a chemical property requires a chemical reaction that will alter what you test: wood  ash

Anything that changes what it “looks like” NOT “what it is” Physical Change A change in shape or state of a substance - crushing, cutting, folding, smashing, melting, boiling… No evidence of a new material forming H O Anything that changes what it “looks like” NOT “what it is”

A chemical reaction has happened! Chemical change A change in the properties of a substance **Means a new substance is formed A chemical reaction has happened! Evidence of a chemical change (and chemical reaction): A change in colour A change in smell 3. Fizzing or bubbling (new gas being made)

This new solid is called a precipitate 4. A new solid forms from a mixture of liquids or the mixture goes cloudy This new solid is called a precipitate A change in energy Exothermic: energy is released (product) Endothermic: energy is absorbed (reactant) “Energy” could be light, heat, sound – think of the most obvious change in energy reaction – an EXPLOSION!

Testing the property can cause a… Physical properties Chemical properties Testing the property can cause a… Physical change Chemical change Δ colour Δ smell Δ energy Gas bubbles Precipitate State or shape NO Reaction Chemical Reaction Same substance with same properties New substance with new properties

Number of protons and neutrons (p+ + no) We will not be building Bohr diagrams this course, but you should remember how do use these numbers Number of protons (p+) [OR electrons (e-) since atoms are neutral] Remember electrons are so small as to be essentially “massless” – the whole mass of the atom is really just the number of p+ and no in the nucleus Number of protons and neutrons (p+ + no)

Atoms that have the same number of protons but a different number of neutrons are called Isotopes. At Mass = 1 At Number = 1 At Mass = 2 At Number = 1 At Mass = 3 At Number = 1 These are ALL considered Hydrogen – based on the proton number

An atom that has lost or gained an electron is called an ion Atoms can either gain or lose electrons Gain - negatively charged ion Lose - positively charged ion H neutral atom H+ positive ion (cation) H- negative ion (anion) An atom that has lost or gained an electron is called an ion

Octet rule: atoms react to acquire a full outer shell: Called valence shell Gain an e- from another atom Lose an e- to another atom Share an e- with another atom Ionic bond Covalent bond Note Metals typically lose e- Non-metals typically gain e-

NOTE These numbers might be called “combining capacity” “valences” or “charges” +1 +3 -3 -2 -1 +2 +4/-4 Non-metals gain e- Metals lose e- Remember: The number of the column is equal to the valence electron number. Know that and you figure out the number of electrons lost or gained – the ionic charge

Mg Cl Cl S Cl Cl MgCl 2 SCl 2 ionic compound covalent compound - +2 - metal non-metal non-metal non-metal MgCl 2 SCl 2 ionic compound covalent compound - +2 Mg Cl Cl S - Cl Cl Gain / lose – called a “formula unit” Sharing – called a “molecule” A compound has different characteristic properties than the atoms which form it.

I Have No Bright Or Clever Friends Diatomic Elements: Elements that are most commonly found in a covalent bond with itself (not as single atoms) I Have No Bright Or Clever Friends I2 H2 N2 Br2 O2 Cl2 F2 NOTE “Greediest” elements that must have a full octet, so they covalently bond with themselves when alone – BUT when bonded to another element there is no longer a reason to be diatomic

Notice: oxygen is not diatomic in a bond… Chemical formula gives the following information: The different elements in the compound The number of atoms in the compound Notice: oxygen is not diatomic in a bond…

Remember the subscript applies to what is directly in front of it Brackets: subscripts outside a bracket multiply by everything inside the bracket. 3 Mg(NO3)2 1 1 Coefficient: total # of molecules present O N Mg O N Remember the subscript applies to what is directly in front of it Mg: 1 · 3 = 3 N: 1 · 2 · 3 = 6 O: 3 · 2 · 3 = 18

Writing Ionic Compound Formula 1. Write the symbol of the metallic element first. 2. Place the combining capacity (charge) of one element as a subscript of the other element. 3. Leave subscripts with a value of 1 out. 4. Reduce the subscripts if possible. beryllium combines with chlorine + 2 - 1 Be Cl Be Cl2 1

Naming Ionic Compounds 1. Write the full name of the metal ion first. 2. Name the non-metal ion dropping the ending and adding the suffix “ide.” beryllium combines with chlorine BeCl2 beryllium chlor ide

Here is an example of “reducing” the subscripts Magnesium combines with Sulfur + 2 - 2 Mg S Mg S magnesium sulph ide Here is an example of “reducing” the subscripts

Transition metals

Transition metals can give away different numbers of electrons. To avoid confusion: Brackets are used to show the number of electrons the Transition metal is giving away.

Fe Cl Fe Cl FeCl2 FeCl3 Iron (III) chloride Iron (II) chloride + 2 - 1 1. Write the symbol of the metallic element first. 2. Place the combining capacity (charge) of one element as a subscript of the other element. 3. Leave subscripts with a value of 1 out. 4. Reduce the subscripts if possible.

Pb O PbO lead oxide (IV) +4 -2 Write the name of the ionic compound: + 1 Pb O PbO 1 2 2 lead oxide (IV) Remember: Always look at the anion to see if it has been reduced. If it has, so has the metal.

Al(C2H3O2)3 Polyatomic Ions (poly = many) Groups of covalently bonded atoms that act as ions. Polyatomic ions function as one unit with one ionic charge – gain or lose electrons. Al(C2H3O2)3 Aluminum Acetate Note the ending (not “ide”) – the ending is the clue that it is polyatomic and NOT a plain element

There are a few “ides” BUT they are obviously not elements

Mg NO3 Mg(NO3) magnesium nitrate Write the name of the ionic compound: + - 1 Mg NO3 Mg(NO3) 2 magnesium nitrate We get the valences (charges) and criss-cross – just like building any ionic compound

Ni(NO3)2 magnesium sulfate KMnO4 iron (III) hydroxide Ca(C2H3O2)2 silver chromate PbCO3 tin (IV) sulfate Na2HPO4 ammonium nitrite nickel (II) nitrate MgSO4 potassium permanganate Fe(OH)3 calcium acetate Ag2CrO4 lead (II) carbonate Sn(SO4)2 sodium hydrogen phosphate NH4NO2

Prefix Number of Atoms mono 1 di 2 tri 3 tetra 4 penta 5 hexa 6 hepta 7 octa 8 nona 9 deca 10 Memorize this…

Writing Covalent Compound Formula 1. Write the symbol of each element. 2. Use a subscript to show the number of atoms as indicated by the prefix. *Do NOT reduce covalent bonds Prefix Number of Atoms mono 1 di 2 tri 3 tetra 4 penta 5 hexa 6 di phosphorus oxide penta P O 2 5

Naming Covalent Compounds 1. Write the first non-metal with the appropriate prefix. *We don’t use “mono” for the first non-metal 2. Write the second non-metal with the appropriate prefix and add the suffix “ide.” N O 2 4 Prefix Number of Atoms mono 1 di 2 tri 3 tetra 4 penta 5 hexa 6 di nitrogen tetra oxide dinitrogen tetroxide

OCl2 oxygen dichloride MgCl2 CuCl2 magnesium chloride Does it have a metal? YES (ionic) Polyatomic NO (covalent) Find charges Criss-cross Don’t change ending Is it a transition? NO charges NO criss-cross Use prefixs Ends in “ide” Fe(NO3)2 iron (II) nitrate NO Find charges Criss-cross Ends in “ide” YES Find charges (reverse) Criss-cross Use Brackets Ends in “ide” OCl2 oxygen dichloride MgCl2 magnesium chloride CuCl2 copper (II) chloride

reactants products 2 + A + 2 B C Chemical reaction – substances react to produce one or more new substances. Chemical equation – contains all necessary information about a reaction. 2 + reactants products A + 2 B C

(l) = liquid (g) = gas (s) = solid *(aq) = aqueous At this level it is expect that you can decipher chemical reactions as word equations: Hydrogen gas and oxygen gas react to form water vapour H + O H2O 2 (g) 2 (g) (g) diatomic State (phase) of the substance is always shown as small subscripts after the compound formula: (l) = liquid (g) = gas (s) = solid *(aq) = aqueous *Aqueous means this compound has dissolved in water

H2 (g) + O2 (g) H2O (g) 2 2 The Law of Conservation of Mass (balancing equations): In any chemical reaction matter cannot be created or destroyed. H2 (g) + O2 (g) H2O (g) 2 2 H H O H H O O H H H H O was This equation is unbalanced because the atoms are not conserved from one side (reactants) to the other (products)

Rules for Balancing Equations Coefficients (phase/state) Subscripts H2 (g) + 1O2 (g) H2O (g) 2 2 Coefficients indicate the ratio of the substances in the chemical reaction. “Two molecules of hydrogen react with one molecule of oxygen to yield two molecules of water.” Coefficients of 1 are not typically written Rules for Balancing Equations You cannot change the formula of any reactant or product. 2. You can only change the coefficients in front of the reactants and products.

2 HCl + MgBr2 MgCl2 + HBr 2 Balanced H: 1 H: 1 (2) = 2 (2) = 2 Cl: 1 Cl: 2 Mg: 1 Mg: 1 Br: 2 Br: 1 (2) = 2 (2) = 2 (2) = 2 (2) = 2 Balancing Tips: Find a way to track it that is meaningful to YOU. Balance metals first, then non-metals. Balance single elements last. Check and recount all the atoms. Prepare for trial and error.

2 LiI + MgO MgI2 + Li2O Balanced Try using a system (here are dots) to track balanced atoms – when all reactants have dots, it’s balanced! 2 LiI + MgO MgI2 + Li2O Balanced Balancing Tips: Find a way to track it that is meaningful to YOU. Balance metals first, then non-metals. Balance single elements last. Check and recount all the atoms. Prepare for trial and error.

2 2 Balanced K(NO3) + Mg Mg(NO3)2 + K Balancing Tips: Find a way to track it that is meaningful to YOU. Balance metals first, then non-metals. If polyatomic ion is intact on both sides – balance as a whole unit. Balance single elements last. Check and recount all the atoms. Prepare for trial and error.

Balanced 2 K2O + Cl KCl + O (s) 2 2 (g) 4 2 (g) Solid potassium oxide and chlorine gas react to produce potassium chloride and oxygen gas. +1 -2 +1 -1 + + potassium oxide chlorine Potassium chloride oxygen 2 K2O + Cl KCl + O (s) 2 2 (g) 4 2 (g) Balanced Strategies: Isolate the reactants and products (look for key words) Write the reactants, reform (re-criss cross) the products The goal is to be able to convert any written equation to an actual equation Balance and include phases/states (if given)

Many reactions are similar. Chemists have classified 5 types of reactions BIG PICTURE IDEA: If you know the reactants - you can guess the type of reaction AND predict the products Synthesis reactions Decomposition reactions Single replacement reactions Double replacement reactions Combustion reactions

You have to “re-criss cross” the product valences too Synthesis Reactions (Combination): 2 or more substances react to form a single substance. A + B  C You have to “re-criss cross” the product valences too 2 K + Cl2 KCl Fe + O2 Fe2O3 2 4 3 2

Decomposition products can be hard to predict Decomposition Reactions: A single compound splits apart, into two or more simpler compounds. C  A + B Decomposition products can be hard to predict CO2 CO + O2 Al2S3 Al + S 2 2 2 3

You have to “re-criss cross” the product valences too Single Replacement Reactions: One element replaces another element in a compound. More active elements replace less active elements. A + BC  AC + B You have to “re-criss cross” the product valences too 2 2 I2 + CuCl Cl2 + CuI Ba + K(NO3) K + Ba(NO3)2 2 2

You have to “re-criss cross” the product valences too Double Replacement Reactions: 2 compounds split and exchange positive ions AB + CD  AD + CB 2 2 BaF2 + LiBr BaBr2 + LiF HCl + AlBr3 HBr + AlCl3 3 3 You have to “re-criss cross” the product valences too

CxHy + O2  CO2 + H2O 8 7 3 5 3 4 C7H6O + O2 CO2 + H2O (Carbon) Combustion Reactions: Oxygen reacts with a carbon compound to produce water, carbon dioxide and heat. CxHy + O2  CO2 + H2O Combustion reactions ALWAYS react with oxygen to produce carbon dioxide and water C7H6O + O2 CO2 + H2O C3H8 + O2 CO2 + H2O 8 7 3 5 3 4

Synthesis A + B  C Decomposition C  A + B Single replacement A + BC  B + AC Double replacement AC + BD  AD + BC Carbon Combustion CxHy + O2  CO2 + H2O