Chemical Bonds And Equation

Types Of Chemical Bonds

Compound substance made of the combined atoms of two or more elements. Chemical formula tells what elements a compound contains and the exact number of the atoms of those elements

Some Common Compounds Vinegar Acetic acid HC2H3O2 Sand Silicon dioxide SiO2 Stomach Acid Hydrochloric acid HCl Cane Sugar Sucrose C12H22O8

Superscript represents oxidation # or how many electrons has gained or lost 2H2O SO42- Coefficient represents the # of units of each substance Subscripts represents # of atoms in a molecule of a particular element Atoms form compounds to become chemically stable. An atom is chemically stable when the outer energy level is complete, or full.

Ionic Bond vs. Covalent Bond Chemical bond force that holds together the atoms in a substance ION positive or negatively charged atom Ionic Bond vs. Covalent Bond loses or gains electrons shares electrons attraction between opposite charges of ions can form multiple bonds between a nonmetal and a between metal & nonmetals nonmetal

Writing Formulas and Naming Compounds

Binary compound compound composed of two elements Oxidation number positive or negative number (on PTable) which indicates how many electrons an element has gained, lost or shared when bonding with another atom. * When writing a formulas for binary ionic compounds, it is important to remember that compounds formed have a net charge of zero.

POLYATOMIC IONS Charged Name Formula 1+ Ammonium NH4+ 1- Acetate C2H3O2- Chlorate ClO3- Hydroxide OH- Nitrate NO3- 2- Carbonate CO32- Sulfate SO42- 3- Phosphate PO43- Polyatomic Ions a positively or group of atoms negatively charged covalently bonded The prefix poly means “many”, so the term polyatomic means “having many atoms”

Prefixes For Binary Covalent Compounds Hydrate a compound that has water chemically attached to its ions and written into chemical formula. Covalent compounds can form more than one compound with each other. Scientist use Greek prefixes to indicate # of atoms of each element in binary compound. Prefixes For Binary Covalent Compounds #atoms 1 2 3 4 5 6 7 8 prefix Mono- di- tri- tetra penta hexa hepta octa

Chemical Reactions

Chemical reaction - a reaction in which one or more are changed to new substances Reactants - substances that are about to react Produced Reactants Products Products - new substances produced Law of Conversation of Mass total starting mass of all reactants equals the total final mass all products.

Chemical equation - uses chemical formulas and symbols to describe a chemical reaction and the product it produces (see below) Symbol Meaning produces or yields (aq) Aqueous (solid dissolved in H2O) + plus Heat Reactants heated (s) solid Light Reactants exposed to light (l) liquid Elec Electric current (g) gas Applied to reactants

4Al (s) + 3O2 (g) 2Al2O3 Coefficients #’s which represents the number of units of each substance in a rxn 4Al (s) + 3O2 (g) 2Al2O3 Subscripts #’s which represent the number of atoms in a molecule of a particular element

Balancing Chemical Equations

Balanced chemical equations have the same number of atoms of each element on both sides of equation * When balancing chemical equation NEVER change the subscripts, instead change the coefficient in front of the compounds needing balanced.

Steps to Balancing a Chemical Equation Step 1: Write a chemical equation for the reaction using formulas and symbols ­­– make sure reactants are on left side and products on right. Step 2: Count the atoms in reactants and products. Step 3: Choose coefficients that balanced the equation. HINT: Generally, if there is an even # of an element on one side and an odd on the other side, place a 2 in front of compound containing odd number of atoms.

Ex. 2NaBr + Cl2 2NaCl + Br2 STEP 3 STEP 1 Na 1 2 1 2 Br 1 2 2 Cl 2 1 2 STEP 2 STEP 4 Step 4: Recheck the numbers of each atom on both sides of and adjust coefficients if necessary – remember NEVER change subscripts.

Chemical RXNS – Types, Rates And Energy

Synthesis reaction - reaction where two or more substances combine to form another substance Decomposition reaction - reaction where one substance breaks down, or decomposes, into two or more simpler substances A+B AB AB A+B

AB + CD AC + BD A + B AC + B or A + BC AB + C Double – displacement reaction - reaction that results in a precipitate, water or gas when a positive ion of one compound swaps with another positive ion of another compound. AB + CD AC + BD Single – displacement reaction - reaction in which one element replaces another in a compound A + B AC + B or A + BC AB + C

Exothermic reactions Endothermic Reactions Chemical reactions involve energy exchange Exothermic reactions Endothermic Reactions reaction in which energy reaction in which heat is released in front of heat energy is absorbed Ex. burning wood, fireworks Ex. Chemical Ice packs explode photosynthesis

Catalyst speeds up a chemical reaction without itself being permanently changed Inhibitor prevents or slows a chemical reaction or interferes with the catalyst