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**Covalent bond** : a chemical bond in which atoms share electrons


 * Electronegativity **: the tendency of atoms to attract electrons of a bond

(both from [|http://chemistry.about.com] 's chemistry glossary)

<<< covalent bond <<< lewis dot structure- Chlorine


 *  NAMING COVALENT BONDS **

1) Elements are listed by lower group first 2) If both elements are in the same group, the lower atomic number element is the first of the bond. 3) 2nd element will end with -ide 4) Prefixes are used to tell how many atoms are in the bond (mono, bi, tri, etc.) 5) First element will only have a prefix if it is more than one.

Ex 1) BF 3 - Boron triflouride Ex 2) Dinitrogen pentaoxide - N 2 O 5

** DEFINING A COVALENT BOND **


 * __Covalent Bonds__**- one or more bonds made between elements when the bond is made by the //sharing of electrons//
 * __Single Bond__**- sharing of 2 electrons between 2 elements
 * __Double Bond__**- sharing of 4 electrons between 2 elements
 * __Triple Bond__**- sharing of 6 electrons between 2 elements

**DRAWING LEWIS DOT STRUCTURES**

1) Draw the Lewis Dot Structure for each element. 2) Place the element having the most unpaired electrons in the center. 3) Bond as many single elements to the center element as possible. (Keep balance as you draw) 4) Create double/triple bonds as necessary to reach the octet for all elements


 * DRAWING IONS (WITH A CHARGE) **

Carbonate (CO 3 )-² The -2 means that you'll have to add two extra electrons to have all elements reach the octet rule.


 *  EXCEPTIONS TO OCTET RULE **


 * elements with 3, 5, & 7 valence electrons
 * can be stable without meeting octet rule
 * 3 w/ 6 electrons bonding
 * 5 w/ 10 electrons bonding
 * 7 w/ 14 electrons bonding


 * ELECTRONEGATIVITY **

- The ability of an atom in a molecule to attract shared electrons to itself.

 COVALENT BONDS GIZMO [|marshall_s_covalentgizmo.doc]

 CHEMICAL BONDING ACTIVITY


 * NOTES 2/6 **

__S-orbital__ • 2 electrons each • 1 bond location • sphere-shaped • σ-sigma bond • first bond area

__P-orbital__ • 6 electrons total • 3 bond locations • Px Py Pz • π-pi bonds • 3 additional areas

hybridization: classifying bonds

s sp sp² sp³ (see electronegativity values notes sheet)

<span style="color: rgb(23, 29, 222);"> <span style="font-size: 120%; color: rgb(23, 29, 222);">**__CHEMICAL EQUATIONS__** <span style="color: rgb(23, 29, 222);"> Their job: to depict the kind of **<span style="color: rgb(247, 2, 2);">reactants ** and **<span style="color: rgb(255, 117, 0);">products ** and their relative amounts in a reaction.


 * <span style="color: rgb(93, 189, 5);">4 <span style="color: rgb(250, 5, 5);">Al <span style="font-size: 70%; color: rgb(250, 5, 5);">(s) + 3 <span style="color: rgb(244, 6, 6);">O <span style="font-size: 70%; color: rgb(244, 6, 6);">2 (g) >>> <span style="color: rgb(93, 176, 7);">2 <span style="color: rgb(246, 115, 4);">Al <span style="font-size: 70%; color: rgb(246, 115, 4);">2 <span style="color: rgb(246, 115, 4);">O <span style="font-size: 70%; color: rgb(246, 115, 4);">3 (s) **

The **<span style="color: rgb(109, 206, 9);">numbers in the front ** are called **<span style="color: rgb(93, 188, 6);">stoichiometric coefficients **. The letters (s), (g), and (l) are the physical states of compounds.

<span style="color: rgb(101, 6, 147);">---Chemical reactions occur when bonds between the outermost parts are formed or broken. ---Chemical reactions involve changes in matter, the making of new materials with new properties, and energy changes. ---Symbols represent elements, formulas describe compounds, chemical equations describe a chemical reactions.

Ex) **C + O2 → CO2**


 * +** ... separates molecules on the same side
 * →** ... reads as "yields"

This reads <span style="color: rgb(255, 0, 106);">"carbon plus oxygen react to yield carbon dioxide."

but you may <span style="font-size: 117.6%; color: rgb(253, 33, 33);">**not** change the subscripts.
 * Because of the principle of the <span style="color: rgb(251, 19, 19);">conservation of matter, an <span style="color: rgb(249, 21, 21); font-size: 110%;">equation must be //balanced//.
 * It must have the same number of atoms of the same kind on both sides.
 * When balancing a chemical reaction you may add coefficients in front of the compounds to balance the reaction,


 * 4 Al (s) + 3 O 2 (g) → 2 Al 2 O 2 (s)**

This equation means 4 Al atoms + 3 O 2 molecules --produces→ 2 molecules of Al 2 O 2

AND/OR

4 moles of Al + 3 moles of O2 --produces→ 2 moles of Al2O2

<span style="font-size: 120%; color: rgb(145, 13, 135);"> __**STEPS TO BALANCING EQUATIONS**__ <span style="color: rgb(40, 77, 10);"> <span style="color: rgb(225, 65, 9);"> There are four basic steps to balancing a chemical equations. <span style="color: rgb(40, 77, 10);">
 * 1) <span style="color: rgb(225, 65, 9);">Write the correct formula for the reactants and the products.
 * 2) <span style="color: rgb(225, 65, 9);">Find the # of atoms for each element on the left side. Compare those against the # of the atoms on of the same element on the right side.
 * 3) <span style="color: rgb(225, 65, 9);">Determine where to place coefficients in front of formulas so that the left side has the same # of atoms as the right for EACH element in order to balance the equation.
 * 4) <span style="color: rgb(225, 65, 9);">Check your answer to see if:
 * <span style="color: rgb(225, 65, 9);">The #'s of atoms on both sides of the equation are now balanced.
 * <span style="color: rgb(225, 65, 9);">The coefficients are in the lowest possible whole # ratios. (reduced)

__ Hints: __
 * Take 1 element at a time, working left to right except for H & O. Save H for the next to last, & O until last.
 * If everything balances except for O, & there is no way to balance O w/ a whole #, double all the coefficients and try again. (Because O is diatomic as an element)
 * (Shortcut) Polyatomic ions that appear on both sides of the equation should be balanced as independent units.

<span style="font-size: 130%; color: rgb(102, 0, 255);">__**SYNTHESIS REACTIONS**__

__**Synthesis**__- combining one or more elements or compounds to form a __single product__

2 Mg (s) + O 2 (g) → 2 MgO (s) S (s) + O 2 → SO 2 (g)

Examples... 1) Beryllium + Oxygen → Beryllium Oxide = BeO

2) Magnesium + Nitrogen → Magnesium Nitride = M 3 N 2

3) Potassium + Chlorine → Potassium Chloride = KCl <span style="color: rgb(229, 11, 11);">
 * __ DECOMPOSITION __**

--- A chemical change occurs in which a single compound breaks down into 2 simpler compounds. --- 2 HgO (s) → 2 Hg (l) + O 2 (g)

Ex) Hydrogen Iodide --- 2 HI (l) → H 2 + I 2

**DECOMPOSING A CARBONATE**

- Anytime you have a compound with carbonate in it, it decomposes the same way.
 * XCO 3 → XO + CO 2

**SINGLE REPLACEMENT**

- A chemical change in which one element replaces a second element in a bond.
 * 2 K (s) + 2 HOH (l) → 2 KOH (aq) + H 2 (g)
 * Zn (s) + Cu(NO 3 ) 2 (aq) → Cu (s) + Zn(NO 3 ) 2 (aq)

1) Zinc + Sulfuric Acid +2.......+1....-2 Zn + H 2 SO 4 → ZnSO 4 + H 2

**DOUBLE REPLACEMENT**

- A chemical change involving an exchange of positive ions between 2 compounds.
 * Na 2 S (aq) + Cd(NO 3 ) 2 (aq) → CdS (s) + 2 NaNO 3 (aq)

**ACID - BASE REACTIONS**

- The neutralizing of an acid with a hydroxide. - Just like a double-replacement reaction; can tell because water is formed as a product. ............................................................water.
 * 2 H 3 PO 4 + 3 Ca(OH) 2 → 6 HOH + Ca 3 (PO 4 ) 2
 * COMBUSTION REACTION**

- Reaction involving the burning of an organic compound - Will always form CO 2 and H 2 O
 * C 3 H 8 + 5 O 2 → 3 CO 2 + H 2 O

<span style="color: rgb(2, 136, 134);">Will a reaction really happen? - Using your Activity Series Chart on Solubility Sheet - This uses electronegativity vales to determine which element "owns" more of the electrons. - If the single element is higher on Activity Series, it will form a new compound. This means it would "own" more of the electron.

Ex) Br 2 + KI → will happen because Br is higher than I Ex) Br 2 + KCl → won't happen because Cl is higher than Br DOUBLE REPLACEMENT REACTIONS **

- When a DR happens one of the two products must be a "g," "s," or water. - Otherwise the reaction won't happen.
 * Na 3 PO 4 (aq) + 3 KCl (aq) → 3 NaCl (aq) + K 3 PO 4 (aq)
 * nothing would happen


 * STOICHIOMETRY**

If you have 34.1 g of CuSO 4, how many moles of CuSO 4 do you have? Cu: 1 X 63.55 S:1 X 32.07 O: 4 X 16.00 159.61 g

34.1 g X (1 mol/ 159.6 g) = 0.214 CoSO4

How many molecules do you have? Write your answers in correct sigfigs.

0.214 molCuSO4 X (6.022 X 10^23/ 1 mol) = 1.29 X 10^23 molecules

__**Conversion of Mass**__ __**Writing Mole Ratios**__ =__2 molNH 3 __= 3 molH
 * The total mass remains constant when comparing reactants and products. (The two will be equal.)
 * H 2 (g) + I 2 (g) → 2HI (l)
 * The total mass of hydrogen and iodine will equal the mass of hydrogen iodide__.__
 * This uses the coefficients of a balanced equation to show the relationship between compounds.
 * N 2 (g) + 3H 2 → 2NH 3 (g)
 * What this means: 1 molN 2
 * Mole → Mole Calculations**
 * How many moles of NH 3 are produced when 0.60 mol of nitrogen reacs with hydrogen? N 2 (g) + 3H 2 → 2NH 3 (g)
 * 0.60 mol N 2 X (2 molNH 3 / 1 mol N 2 ) = 1.20 mol NH 3

If you form 3.1 mol of water, how many moles of H 2 did you begin with? (Write the balanced synthesis first.)

2 H2 + O2 → 2 H2O 3.1 mol H2O X (2 mol H2 / 2 mol H2O) = 3.1 mol H2

__**Moles - Grams**__ You can covert from grams → mol → grams using the mol:mol ratios. If you have 3.21 g of N2, how many g of NH3 will b produced?
 * N2 (g) + 3H2 (g) → 2 NH3 (g)
 * 3.21 gN2 X (1 molN2 / 28.02 gN2) X (2 molNH3 / 1 molN2) X (17.03 gNH3 / 1 mol NH3) = 3.90 gNH3

__**LIMITING & EXCESS REAGENTS**__

---In a chemical reaction, one compound drives how long and how much a reaction can occur. ---Limiting - determines how much product can be formed ---Excess__ - some left over during the reaction process


 * HOW-TO**

---Convert the grams of each reactant into moles of the product.**<span style="color: rgb(255, 0, 0);"> ---The smaller mole value tells you which starting reactant is the limiting reactant. ** ---Use the moles of the limiting reagent to calculate the amount of product produced.
 * Ex) Copper reacts with S to form copper I sulfide according to the following equation. 2 Cu + S → Cu2S
 * What is the limiting reagent when 80.0 g Cu reacts with 25.0 g S?

--- Cu produces 0.629 moles Cu2S --- S produces 0.779 Cu2S --- Therefore, Cu is the limiting reagent and must be used to answer all questions.
 * -Cu < S:**

--- NOW WHAT? Solve the problem using Cu moles. This will tell you how much product can be formed.

<span style="font-size: 150%; color: rgb(255, 0, 106);">GRAHAM'S LAW SIMULATIONS