Intro to Chemistry

Atoms All matter is composed of atoms. Atoms are arranged in to regions Electron Cloud Electrons  negative particles; No mass Nucleus Consists of: Protons  positive particles; Mass of 1amu Neutrons neutral particles; Mass of 1amu

Atoms Atomic Number Atomic Mass # of Protons Used to Identify an Atom # of Protons = # of Electrons Atomic Mass # of Protons + # of Neutrons

Elements Consist of only one type of atom. 94 elements are found in nature. At least 24 are made in a laboratory.

CHNOPS 98% of the mass of every living organism is composed of just six elements: Carbon C Hydrogen H Nitrogen N Oxygen O Phosphorus P Sulfur S

Electrons The behavior of the electrons determine whether a chemical bond will form and what shape the bond will have. These are 2 key properties for determining biological changes and structure. Electrons fill energy levels to become stable The outermost energy level is called the valence shell. Atoms want their valence shell full Hydrogen and Helium want 2 valence electrons. (Duet Rule) Almost every other atoms wants 8 valence electrons. (Octet Rule)

Bonding Atoms will interact with each other to fill the valence shell. When atoms interact the form stable associations called Molecules. They do this by sharing electrons or gaining and losing electrons.

Covalent Bonds Formed when two atoms share valence electrons.

4 important aspects of Covalent bonds: Orientation: Gives molecules their three-dimensional geometry which contribute to their biological function. Strength & Stability: Covalent bonds are very strong. This leads to stability for biological molecules. Multiple Covalent Bonds: Single bond  sharing of a pair of electrons. Double Bond  involves the sharing of four electrons. Triple bond rare, sharing of 6 electrons. Nitrogen gas

4 important aspects of Covalent bonds: Unequal Sharing of Electrons: If atoms sharing are the same element then they will share the electrons equally. When atoms sharing are different elements they may not share equally. Electronegativity The attraction to electrons. The higher the number the more likely they will attract electrons from another atom.

Polar Molecules Unequal sharing of electrons between 2 atoms.

Polar –vs- Nonpolar Like molecules will interact with each other. Hydrophilic “Water-Loving” Polar molecules interacting with water. Water is a solvent for polar molecules. Hydrophobic “Water-Hating” Nonpolar molecules do not interact with water this way. Nonpolar molecules tend to aggregate together.

Hydrogen Bonds Form between molecules with polar covalent bonds. Intermolecular Force Strongest of all intermolecular forces, but still very weak. However many hydrogen bonds together have considerable strength.

Hydrogen Bonds Hydrogen Bonds greatly influence the structure and properties of the substances. Play important role in determining and maintaining the three-dimensional shapes of giant molecules.

Ionic Bonds Ions An electrically charged particle that forms when one atom loses electrons and another atom gains electrons. One atom becomes positive CATION (loses negative electrons) One atom becomes negative ANION (gains negative electrons) The two opposing charges are attracted to each other resulting in a bond. Weaker bond than covalent bonds. Dissolve in water.

Organic Molecules Molecules containing Carbon Carbon is found in all living organisms Carbon has the ability to bond to 4 other atoms forms very complex molecular structures Carbon skeletons can vary in length, branching, and ring structures.

Water Plays a vital role in living systems as a universal SOLVENT. A liquid in which other molecules dissolve.

Water Heat Capacity The amount of heat required to raise the temperature of water by one degree. Water has one of the highest. At any given time a water molecule forms on average 3.4 hydrogen bonds. This allows for an high amount of heat to be absorbed by water. The large amount of water in living tissues shields the organism from fluctuations in environmental temperatures.

Water Heat of Vaporization Heat required to change water from a liquid to a gas. Most of the heat is used to break the multiple hydrogen bonds so water has a high heat of vaporization temperature. Heat is absorbed from the environment that comes in contact with the water. This acts as a cooling system. Sweating Swamp coolers

Water Cohesion Adhesion The capacity of water molecules to resist coming apart from one another when placed under tension. Occurs between water molecules Adhesion Hydrogen bonding between water molecules and the solid surface surrounding them.

Water Surface Tension The tension on the surface of water due to the hydrogen bonding of the water molecules.