I. Basic Chemistry

A. Elements and Atoms 1. Elements- Substance which cannot be broken down into a simpler substance a) 96% of all life is Carbon, Hydrogen, oxygen and nitrogen b) 3.2% Calcium, Phosphorous, Potassium and Sulfur

2. Atom- The smallest particle of an element a) Atomic structure 1. Proton- positively charged. In nucleus. 1 Dalton mass 2. Neutron- neutral charge. In nucleus. 1 Dalton mass 3. Electron- negative charge. Orbits nucleus. 1/2000 Dalton mass

b) Electron Energy Levels Energy LevelMaximum Number of Electrons 1 st (K) 2 nd (L) 3 rd (M) 4 th (N) 2) However, the outer energy level: valence shell will never hold more than 8 electrons 1) 2 electrons 8 electrons 18 electrons 32 electrons

3. Periodic Table- Chart of Elements arranged by proton number and valence electrons 8 O Oxygen 15.9 e) Neutron Number = Atomic mass – Atomic number a) Atomic Number- indicates the number of proton which determines the the element b) Symbol- Identifies the element c) Atomic Mass- the mass of the atom in Daltons. d) Atoms are Neutral- Therefore the number of proton and electrons are equal

4. Bohr Diagrams- illustrations of an atom. Example: Oxygen 8p 8n 6e 2e 5.Isotopes- Atoms with extra neutrons. Some are unstable and give off radiation as they decay Number of electrons in 2 nd energy level Electrons in the first energy level Nucleus with the number of protons in & neutrons

Electrons are really in Orbitals- the actual path the electron follows 90% of the time No more than two electrons can occupy the same orbital The 1 st energy level contains 1 orbital and therefore holds a maximum of 2 electrons. It is called the 1s orbital and it is spherical The second energy level contains a maximum of 4 orbitals. A spherical 2s and 3 dumbbell shaped orbitals in the X, Y, and Z axis called the P1, P2 and P3 orbitals

Electrons fill lower energy levels before moving to higher energy levels

B. Chemical Bonding 1. Compound- two or more elements chemically combined 2. Molecule- smallest particle of a compound 2H 2 OCO 2 C 2 H 5 OHC 6 H 12 O 6 Atoms Elements Molecules

What Determines Whether Atoms Bond? 3. Atoms with their outer energy level filled are stable. He, Ne, Ar, Kr, Xe, Rn (Noble Gasses). Keep in mind that helium’s first energy level is its outer energy level and therefore requires only two electrons in its valence shell for stability 4. Unstable atoms will share or transfer electrons to become stable

C. Covalent Bonding- Sharing a pair of electrons to fill the outer energy level p p P8 n8 2e- e- Oxygen Hydrogen e-

D. Ionic Bonding- The transfer of electrons from one element to another to fill the outer energy level 1. Electronegativity- a measure of the attraction of electrons to an atom. 2. When atoms with high electronegativities are placed with atoms with low electronegativities (the difference is greater than 1.67), Ionic bonding occurs a) The transfer of the electron from one atom to another causes the formation of particles called ions b) Ions with opposite charges attract

Example of Ionic Bonding Sodium’s valence = Sodium’s Electronegativity = Chlorine’s valence = Chlorine’s Electronegativity = Electron Transfer Electronegativity Difference = 2.23 > 1.67 Attraction SodiumAtom Chlorine Ion

E. Hydrogen Bonds- weak bonds between polar moleculesHydrogen Bonds- 1. When atoms with different electronegativites covalently bond, electrons are shared unequally resulting in polar covalent bonds. 2. Hydrogen bonds can then for between the molecules or even parts of large molecules like DNA and proteins

F. Chemical Reactions- breaking of existing bonds and the formation of new ones 1. Activation Energy- energy needed to start a reaction. (heat, stirring, electric.) Activation Energy- 2. Atoms cannot be created or destroyed in a chemical reaction, they are only rearranged into different molecules

3. Example: H 2 + O 2  H 2 O Reactants yields Products 2H 2 + O 2  2 H 2 0 coefficient Subscript

4. Endergonic Vs Exergonic Reactions