1. Chemical Bonds and Equations
Physical Science

2. Why do atoms form chemical bonds?
Question:
Why do atoms form chemical bonds?

3. Types of Chemical Bonds-11/18/14
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 these elements

4. Some Common Compounds
Vinegar
Acetic acid
HC2H3O2
Sand
Silicon dioxide
SiO2
Stomach Acid
Hydrochloric acid
HCl
Cane Sugar
Sucrose
C12H2208
Atoms form compounds to become chemically stable. An atom is chemically stable when the outer energy level is complete, or full.

5. * ION- positive or negatively charged atom
Chemical bond- force that holds together the atoms in a substance
* ION- positive or negatively charged atom
Ionic Bond
Covalent Bond
Loses or gains electrons
Attraction between opposite charges of ions
Between metal & nonmetal
Shares electrons
Can form multiple bonds
Between a nonmetal and a nonmetal

6. Ionic and Covalent Bonding

7. What would a chemist name the compound CuCl?
Question:
What would a chemist name the compound CuCl?

8. Writing Formulas & Naming Compounds -11/20/14
Binary compound- compound composed of two elements Oxidation number- positive or negative number which indicates how many electrons an element has gained, lost or shared when bonding with another atom *When writing formulas for binary ionic compounds, it is important to remember that compounds formed have a net charge of zero.

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

11. Prefixes for Binary Covalent Compounds
Hydrate- compound that has water chemically attached to its ions and written into its chemical formula.
Covalent compounds can form more than one compound with each other. Scientists use Greek prefixes to indicate # of atoms of each element in binary compound.
Prefixes for Binary Covalent Compounds
# of
Atoms 1 2 3 4 5 6 7 8
Prefix
Mono-
Di-
Tri-
Tetra-
Penta-
Hexa-
Hepta-
Octa-

12. Why do chemical equations need to be balanced?
Question:
Why do chemical equations need to be balanced?

13. Chemical Reactions -12/2/14
Chemical reaction- a reaction in which one or more substances are changed to new substances
Reactants- substances that are about to react
Products- new substances produced
Law of Conservation of Mass- total starting mass of all reactants equals the total final mass of all products.
Reactants Produce Products

15. Chemical equation- uses chemical formulas and symbols to describe a chemical reaction and the product it produces
Symbol
Meaning 
Produces/yields
(aq)
Aqueous (solid dissolved in H2O) +
plus
Heat
Reactants heated
(s)
solid
Light
Reactants exposed to light
(l)
liquid
Elect
Electric current applied to reactants
(g)
gas

17. *Review: Coefficients- numbers which represent the number of units of each substance in a reaction Subscripts- numbers which represent the number of atoms in a molecule of a particular elements

18. Balancing Chemical Equations-12/9/14
Balanced chemical equations- have the same number of atoms of each element on both sides of equation *When balancing chemical equations NEVER change the subscripts, instead change the coefficient in front of the compounds needing to be balanced.

19. Steps to Balancing a Chemical Equation
Write a chemical equation for the reaction using formulas and symbols—make sure reactants are on left side and products on right.
Count the atoms in reactants and products.
Choose coefficients that balance 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.
Recheck the numbers of each atom on both sides of equation and adjust coefficients if necessary— remember NEVER change subscripts.

20. Example: Video: https://www.youtube.com/watch?v=Q4WWiAm3nPM

21. What happens to chemical bonds during energy exchanges?
Question:
What happens to chemical bonds during energy exchanges?

22. Chemical Reaction Types-12/9/14
Synthesis reaction – reaction where two or more substances combine to form another substance A + B  AB Decomposition reaction – reaction where one substance breaks down or decomposes into two or more simpler substances AB  A + B

23. Single displacement reaction- reaction in which one element replaced another in a compound. A + BC  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

24. Chemical reactions involve energy exchange
Exothermic Reactions
Endothermic Reactions
Reaction in which energy is released in form of heat
Ex. Burning wood, fireworks, elephant’s toothpaste
Reaction in which heat energy is absorbed
Ex. Chemical ice packs, photosynthesis
Catalyst- speeds up a chemical reaction without itself being permanently changed
Inhibitor- prevents or slows a chemical reaction or interferes with the catalyst