Chapter 3

Chapter 3

Chapter 3 FORMULAS AND NAMES! Although there are only just over 100 elements, there are millions of different compounds! Elements combine! Only the noble gases tend to exist as isolated atoms (think noble = snobby) Monatomic: consist of single atoms (mono = one)

Two main types We talk about two main types of compounds. Classified by the BONDS they form! IONIC COMPOUNDS: one element loses electrons, one gains. CHARGED IONS COME TOGETHER TO BE NEUTRAL. FORMED FROM IONIC BONDS MOLECULAR COMPOUNDS: formed from COVALENT BONDS. Atoms SHARE electrons

Ions and Ionic Compounds Ions: Atoms or groups of atoms with a positive or negative charge This is where its important to know your valence electrons! These are the outermost electrons of an atom Use your periodic table to figure it out! Group 1a has 1 valence electron Group 8 has 8 valence electrons (ex is He=2) Atoms want 8 valence electronsso, will gain or lose!

Cation: ion with a positive charge (has lost an electron), generally groups 1a, 2a, 3a Sodium, Na, Group 1a, 1 valence electron Remember, atoms want to get to 8 valence electrons Ask yourself: is it easier to lose 1 electron or gain 7? Sodium will generally LOSE one electron= +1 charge Na+1 What about Magnesium? Lithium? What about Hydrogen?

For metallic elements, the name of the cation is the same as the name of the element Sodium atom forms a sodium cation Symbol = Na+1 Metals tend to have very different properties from their cations Sodium metal is explosively reactive with water Sodium cation is in table salt, stable in water Anions

Anions: Atoms that have gained one or more electrons and have a NEGATIVE charge Ex: Chlorine, group 7a, has 7 valence electrons Ask yourself: is it easier to gain one electron or lose 7? Gain 1= Cl-1 Chlorine Ion will gain one electron, -1 charge The name of an ion usually ends in ide So a chlorine ion will be called chloride Ionic Compounds

Ionic Compounds: Compounds made up of cations and anions Usually composed of metal cations and nonmetal anions Ionic compounds are electrically neutral How Is this possible if they are made up of charged atoms??? Polyatomic Ions Poly-many

Polyatomic ions: tightly bound groups of atoms that behave as a unit and carry a charge. The names of most of the polyatomic ions end in ite or -ate : sulfite (SO3- and SO4-) Charge for each ion is the same, different numbers of O TABLE ON THE BACK OF YOUR PERIODIC TABLE!!! Formula Units: lowest whole number ratio of ions in an IONIC COMPOUND

Think: metal and nonmetal! Not a molecule. 3 dimensional patterns of ions Think Salt NaCl Writing Ionic Formulas! (Yay!!!!) Ionic = METAL AND NONMETAL! Ionic bond = swap of electrons Metals lose, nonmetals gain, COMPOUND IS NEUTRAL!!!!!

Binary Ionic Compound : (2 elements) 1. Write the symbols 2. Find the charges (periodic table) 3. Criss-Cross 4. Reduce if necessary Ternary Ionic Compounds: Compound that contains atoms of three different elements Polyatomic Ions! How to write the formula:

1. Write the Symbols 2. Surround the Polyatomic Ion in parentheses (think: PUT IT IN A BUBBLE) 3. Write charges 4. Criss Cross (charge goes OUTSIDE parentheses Ionic Charges For monatomic ions, look at the periodic table We know how to do this already! For Transition metals, many have more than

one charge! I have to give you the charge Fe(II) ion (Read: Iron two ion) Roman numeral gives you the charge Naming Ionic Compounds Binary: 1. Write the name of the metal (include roman numeral for transition metal) 2. Write the name of the nonmetal ending with ide Sodium Chloride, Iron (II) Oxide

Ternary: 1. Write the name of the cation (usually a metal, but ammonium (NH4) is a cation 2. Write the name of the anion (if polyatomic, just write the name on the chart, if nonmetal, end in ide) WRITE THE FORMULAS copper (II) acetate sodium hydroxide lithium oxide

cobalt (III) carbonate aluminum sulfide sodium cyanide iron (III) phosphide vanadium (V) phosphate sodium permanganate manganese (III) fluoride Name the Compounds!

Na2CO3 Al2S3 PbO Al(CN)3 Mg3P2 NH4OH KCl FeCl3

Molecular Compounds (AKA COVALENT) Binary molecular compounds 2 NONMETALS How can we tell the different compounds? Prefixes!!! To Name a Molecular compound: Use prefixes to tell me how many of each atom

Name end in ide CO= carbon monoxide CO2= carbon dioxide You can leave the mono off of the first element, but not the second Molecular compounds: compounds composed of molecules. Generally 2 nonmetals Most have low melting or boiling points so most exist in liquid or gas state at room temperature

Carbon Monoxide Carbon Dioxide Dihydrogen Monoxide (see a pattern in naming? Well get to that later) Molecular Formulas YAY!!!! Molecular compounds involve electron SHARING But they can share in multiple ways!

Think of CO and CO2 = both would be named carbon oxide if we used ionic rules Molecular compounds = TWO NONMETALS How can you tell two molecular compounds apart? PREFIXES Know Your Prefixes!!! Mono = 1 Di = 2 Tri = 3

Tetra = 4 Penta = 5 Hexa = 6 Hepta = 7 Octa = 8 Nona = 9 Deca = 10 You must know these prefixes for the test! I will

not give them to you So, to write the formula of a molecular compound, just decode the prefixes Dihydrogen monoxide Di = 2 hydrogen Mono = 1 oxygen Formula is H2O Exceptions:

If there is only one atom of the first element, you dont need the prefix mono (still need it for the second element, though) If the element starts with a vowel, drop the 2nd o on mono Monoxide, not monooxide Naming Molecular Compounds Use prefixes to indicate number of atoms End second element in -ide

Example: OF2 = oxygen difluoride (no mono on first element) Cl2O8 = dichlorine octaoxide Molecular formulas Just use the prefixes to tell you how many of each atom! Carbon tetrafluoride = CF4

Dihydrogen monoxide = H2O The tricky part!!! Ionic : metal and nonmetal, get charges and criss cross, NO prefixes Molecular: two nonmetals, no charges, use PREFIXES Naming Acids

Acids are compounds that release H1+ ions when dissolved in water. Look for compounds with a hydrogen in it Technically a molecular compound, but. Naming Acids 1. Name using ionic rules 2. If ends in -ide, add hydro to the beginning and -ic acid to end 3. If ends in -ite, add -ous acid to the end

4. If it ends in ate, add -ic acid to the end HCl 1. Hydrogen chloride Hydrochloric acid H2SO3 2. Hydrogen sulfite Sulfurous Acid H2SO4 3. Hydrogen sulfate

Sulfuric Acid THINK! Aight, its us (ite => ous) I ate something ick! (ate => ic) More with the MOLE! Would it be practical to count each grain of sand? Why or why not?

You can measure matter by number, mass, or volume We have units that measure the amount of something: dozen=12 Mole (mol): SI unit that measures amount 6.02 x 1023 representative particles of something (usually atoms, molecules or formula units) Representative Particles and Moles Substance

Representative Particle mole Atomic Nitrogen Atom N Chemical Formula # particles in one

6.02 x 1023 Nitrogen Gas Molecule N2 6.02 x 1023

Water Molecule H2O 6.02 x 1023 Calcium Ion

Ion Calcium Fluoride Sucrose Ca2+ 6.02 x 1023 formula unit CaF2

Molecule C12H22O11 6.02 x 1023 6.02 x 1023 Atom to Mole Conversions Since it is much easier to refer to a quantity of atoms/ representative units instead of a singular

atom/representative unit, we can convert # of atoms to MOLES and moles to # of atoms! 1. Start with your known 2. Use a conversion factor 3. What you want goes on the TOP! 4. LABEL EVERYTHING!!! Lets TRY it! How many moles of magnesium is 1.25 x 1023 atoms of magnesium?

1. Start with your known: 1.25 x 1023 atoms of magnesium 2. use a conversion factor: 1 mol Mg/ 6.02 x 1023 atoms of Mg 3. What you WANT goes on TOP 1.25 x 1023 atoms of magnesium x 1 mol Mg/ 6.02 x 1023 atoms of Mg More Practice: How many moles is 2.80 x 10 24 atoms of

silicon? How many molecules is 0.360 mol of water? Atoms in a Mole of a Compound You can also calculate the number of atoms in a mole of a compound Same steps, just do it twice! Moles => representative unit => atoms

Lets Try it! How many atoms are in 2.12 mol of propane (C3H8)? Moles => molecules =>atoms (2 calculations!) 2.12 mol C3H8 x 6.02 x 1023 molecules C3H8/1 mol C3H8 How many atoms in one molecule of C3H8??? 3 carbons + 8 hydrogens = 11 total atoms 1.27 x 1024 molecules of C3H8 x 11 atoms / 1 molecule C3H8 Answer is 1.40 x 1025 atoms

More Practice! 1. How many atoms in 1.14 mol of SO3? 2. How many atoms of C, H, and O are in 3.65 moles of C12H22O11? Calculating Empirical Formulas Empirical Formula: the lowest whole-number ratio of the

atoms of the elements in a compound. To calculate the empirical formula from experimental data: Calculate the moles of each element in the compound Identify the smallest mole value Divide all mole values by this smallest number This should give you a whole number (this is a comparative ratio!) Molecular Formulas You can determine the molecular formula if

you know the empirical formula and the molar mass of the unknown compound Just take molecular mass/empirical mass. This will give you a whole number by which to multiply the subscripts! Empirical Formula Practice A compound containing nitrogen and oxygen is decomposed in the laboratory and produces 24.5 g nitrogen and 70.0 g oxygen. Calculate the

empirical formula of the compound Grams Moles RATIO! Molecular Formula Practice A compound contains carbon, hydrogen, and oxygen. The empirical formula is C2H3O and the molar mass is 86.09 g/mol. Find the molecular formula. Find empirical mass. Divide molecular mass by

empirical mass to get whole number multiple. Formulas from Combustion Analysis 1. Write down the masses of each combustion product and the mass of the sample (if given) 2. Convert the masses of CO2 and H2O to moles 3. Convert the moles of CO2 and H2O to moles of C and H 4. If the compound contains and element other than C and H, find the mass of the other element by subtracting the sum of the masses of C and H from the mass of the sample. Convert this mass to moles

5. Write down temp. formula (moles = subscript) 6. Divide each subscript by the smallest number 7. If not whole number subscripts, multiply to get a whole number Chemical Reactions In a chemical reaction, one or more substances changes into one or more different substances. Reactants -> Products -> is read as yields

As reactants are converted to products, the bonds holding the atoms together are broken and new bonds are formed. Law of conservation of mass applies here! Although bonds are broken and reformed, the atoms are neither created nor destroyed. How can you tell a reaction has occurred? Formation of gas(bubbles), heat is given off or absorbed(hot or cold), or formation of a

precipitate (floaty stuff) Chemical Equations We use formulas to write chemical equations to describe reactions Skeleton equation: unbalanced formula To indicate the physical state of the substance: (s) is solid, (l) is liquid, (g) is gas, and (aq) is aqueous solution (disolved in water) Catalyst: used to speed up a reaction, but not used up during the reaction. Written on top of the yields arrow Heat can also be used to produce a reaction and is indicated above

the arrow Diatomic elements Some elements always occur in pairs if in a pure state. HONClBrIF H2 O2 N2 Cl2 Br2 I2 F2 Balancing Equations

RULES 1. Write the correct formulas for the products/reactants and their physical states (if known) 2. Reactants on left, products on right, separated by yields arrow 3. Balance the elements one at a time by using a coefficient 4. Make sure coefficients cant be reduced

Word Equations You can write an equation from a word description! You MUST KNOW YOUR FORMULAS! 1. Write the formulas for the reactants (watch for diatomics!!!) 2. Write a yield arrow 3. Write the formulas for the products (watch for diatomics! 4. Balance the equation!!!!!

Types of Chemical Reactions 5 main types Synthesis (combination), Decomposition, Single Replacement, Double Replacement, Combustion Combination Reactions: (also called SYNTHESIS reactions, synthesis=make something) A + B => AB (look for one product)

Decomposition reactions Decomposition reactions are when a compound breaks down into simpler compounds/elements Decomposition means TO BREAK DOWN AB => A + B Look for one REACTANT Most require some sort of energy input

Single Replacement Reactions In single replacement reactions, one element replaces another element in a compound. A + BC => AC + B Metal will replace metal, nonmetal will replace nonmetal Depends on the reactivity of the element Activity Series: lists elements in order of reactivity. More reactive elements will replace less reactive elements.

Double Replacement Reactions Double replacement reactions involve an exchange of positive ions between two ionic compounds. The metals switch places AB + CD => AD + CB When rewriting the new compounds, metals still come first!

Combustion Reactions Combustion reactions occur when a compound reacts with oxygen to produce carbon dioxide and water. Often produces heat and light (burning) Equation will always be the same (only the starting compound will change) Compound + O2 => CO2 + H2O

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