1.  You need to study your notes and vocab.  Make sure you know the following things:  What is a period? What does it represent?  What is a family? What does it represent?  What is atomic mass?  If you know the atomic number and atomic mass, what else do you know?

2.  Selenium’s (Se) atomic number is 34. Its atomic mass is 79. Its period is 4, its family is 6.  On your paper, answer the following questions: 1. How many protons does Se have? 2. How many electrons does Se have? 3. How many neutrons does Se have? 4. How many orbitals does Se have? 5. How many electrons are in its outer orbital?

3. C2.a

4.  Atoms in compounds are held together by bonds.  This is where electrons become important…

5.  The octet rule states that elements gain or lose electrons to attain an electron configuration of the nearest noble gas. Remember, the noble gases are Family 8, so they have 8 electrons in their outer orbital.

6.  Valence electrons are electrons that are available to form bonds.  They are the electrons furthest to the outside of the atom (outer orbital).  The electrons that are the nearest to the nucleus are held more tightly than those farther away and cannot leave orbit.

7.  Remember when I said atoms like to have equal numbers of protons and electrons.  Well… that’s not always the case…  An ion is an atom or molecule with a net electric charge (either positive or negative) due to the loss or gain of one or more electrons.

8.  An atom that gains an electron has a negative charge.  An atom that loses an electron has a positive charge.

9.  An ionic bond is a bond formed when electrons are transferred from one atom to another (gain/lose e-); the attraction between oppositely charged ions.  Usually when metals bond with nonmetals.

11.  A covalent bond forms when electrons are shared between atoms.  Usually when nonmetals bond together.

13.  Not actually a bond.  Chemical attraction in which the proton of a hydrogen atom of one molecule is attracted to an electronegative atom of another molecule.  Think H 2 O (water).  These bonds are weaker attractions than covalent or ionic bonds.

14.  Hydrogen bonds have to involve hydrogen.  Will also involve an electronegative atom such as N (nitrogen), O (oxygen), or F (fluorine).

16. C2.a

17.  A chemical reaction involves either the making or breaking of chemical bond.  This is a process that changes one set of chemicals into another set of chemicals.

18.  These occur slowly:  Iron + Oxygen -> Iron Oxide (rust)  Or they can occur quickly:  Hydrogen gas + Oxygen -> EXPLOSION

19.  The elements or compounds that enter into a chemical reaction are called reactants.  The elements or compounds that are produced by a chemical reaction are called products.  H 2 O + CO 2 -> O 2 + C 6 H 12 O 6 Reactants Products

20.  Law of Conservation of Energy: energy can neither be created nor destroyed…  So energy is released or absorbed whenever a chemical bonds are broken or formed.

21.  Since atoms aren’t typically destroyed or created, you must have the same number of an element before and after a chemical reaction occurs.  This is called balancing chemical equations.

22.  Subscripts: little numbers; come after the element; represent the number of atoms of that elements; CANNOT be changed.  Coefficients: big numbers; come at the beginning of an element or compound; think multiplication; CAN be changed.

23.  Add coefficients in front of the compounds to balance the following equation:  H 2 O + CO 2 -> O 2 + C 6 H 12 O 6