Chap 2.docx

**CHAPTER 2** ============= CHEMICAL CONTEXT OF LIFE ======================== **Atomic Structure** \>\>\>\>\>An understanding of chemistry is important because an interaction between atoms is one of the lowest levels of biological organization. \-\--**matter** \-\--**mass** \-\--**element** O...

**CHAPTER 2** ============= CHEMICAL CONTEXT OF LIFE ======================== **Atomic Structure** \>\>\>\>\>An understanding of chemistry is important because an interaction between atoms is one of the lowest levels of biological organization. \-\--**matter** \-\--**mass** \-\--**element** O = oxygen \-\-\-\-\-- N = nitrogen About 96% C = carbon H = hydrogen \-\-\-\-\-- K = potassium \-\-\-\-\-- S = sulfur P = phosphorous Ca = calcium Na = sodium Remaining 3.7% Cl = chlorine Mg = magnesium Trace elements \-\-\-- \-\--**Trace elements** \-\--**atom** **\ ** **CHARACTERISTICS OF ATOMS** \>\>\>\>\>Atoms are made up of subatomic particles. The 3 most stable subatomic particles are: neutrons, protons, and electrons. (see fig 2.4) \-\--**Protons** \-\--**Neutrons** \-\--**Electrons** \-\--**Dalton** is a mass unit for subatomic particles. 1 Dalton = 1.67 x 10^-24^g \-\--**atomic number** \-\--**atomic mass** or **mass number** **Electrons, Orbitals, and Electron Shells** \-\--**Electron orbitals**(see fig 2.8) \-\--**electron shells**(see fig 2.8) \-\--**Energy** \-\--**Potential energy** \-\--**Valence electrons** \-\--**valence shell** **Ions, Ionization, and Isotopes** \-\--**Ion** **\-\--Ionization** \-\--**Anion** \-\--**Cation** \-\--**Isotopes** \-\--**Radioisotopes** **Bonding and Electronegativity** \>\>\>\>\>\>\>A reactive atom will try and fill the valence shell by interacting with other atoms. This interaction (**bonding**) may result in two atoms forming a **chemical bond** (see fig 2.9). \-\--**Chemical bond** \-\--**Compound** \-\--**Molecule** \-\--**Molecular formula** (see fig 2.10) \-\--**Structural formula** (see fig 2.10) \-\--**Electronegativity** **Ionic and Covalent Bonds** If the electronegativity of an atom is much greater than the electronegativity of another atom that an electron transfer will occur. The atom with the lower electronegativity will transfer an electron to the atom with the greater electronegativity. After the transfer both atoms will have a charge. \-\--**Ionic bond** \>\>\>\>\>**Covalent bond** is a bond formed when two atoms share a pair of valence electrons (see fig 2.9) \-\--**Single covalent bond** \-\--**Double covalent bond** \-\--**Triple covalent bond** **Nonpolar Covalent Bonds, Polar Covalent Bonds and Hydrogen Bonds** \-\--**Nonpolar covalent bond** \-\--**Polar covalent bond** (see fig 2.11) \-\--**Hydrogen bond** (see fig 2.14) Chemical reactions involve making and breaking chemical bonds \-\--**Chemical reactions** \-\--**reactants** \-\--**products** \-\--**Chemical equilibrium** Tennis court analogy of chemical equilibrium PERSON "A" \| PERSON "B" Picks up the balls as \| Picks up the balls very quickly as possible \| leisurely and slowly hits Even if "A" starts with all the balls equilibrium will be reached where "B" will have most but not all of the balls and the rate of balls crossing the net (how many per minute) will be equal. What if the conditions change: "A" still hits as quick but only get half over the net? The equilibrium shifts so that "B" has fewer balls than before and "A" has more. A new equilibrium - equal rate of balls crossing the net -- is achieved.