Chapter 2 Chemical Foundations of Life

2.1 The Building Blocks

Matter Atoms are the smallest unit of matter Atoms cannot be broken down chemically Different atoms are called elements Each element has a unique atomic number which is its number of protons

Parts of an atom Nucleus contain protons and neutrons – both contribute to the atoms mass Changing the number of neutrons changes the mass but not the elements properties Different masses of the same element are called isotopes. Some isotopes (radioisotopes) are unstable and break down (decay) into other elements Some radioisotopes are useful to investigate chemical processes other are used to determine the age of certain materials

Electrons Electrons are negative particles which reside in regions outside of the nucleus. Adding or removing electrons makes the atom an ion which can positive or negative. Whether an element gains or loses electrons determines its chemical properties.

Bonding Positive ions form when an atom transfers electrons to another atom. These oppositely charged atom attract forming a ionic bond. Some elements don’t transfer but share their elections with other atoms creating a covalent bond. Unevenly shared electrons makes bonds polar giving it slightly positive and negative “pole”

2.2 Water

Water as a solvent The polarity of individual water molecules attracts them to one another This type of interaction is called a hydrogen bond Nonpolar molecules (like oils) do not form H- bonds and do not mix well with water.

Water stabilizes temperature Because of hydrogen bonding, it takes a lot heat to raise the temperature of water (high heat capacity) Water absorbs heat when it evaporates and releases heat when it is condenses When water freezes, the molecules lose energy and spread apart

Water and pH Water spontaneously separate into hydrogen ions (H+) and hydroxide ions (OH–) Water has equal concentrations amounts of H+ and OH- pH: measure of the hydrogen ions in a solution Base: accepts hydrogen ions in water pH above 7 Acid: releases hydrogen ions in water pH below 7

2.3 Carbon

Carbon forms 4 covalent bonds Organic compounds - chains or rings or carbon and hydrogen. Wide variety of compounds: Methane – one carbon Octane – in gasoline Beneze – ring of 6 carbons Buckminster Fullerene – 60 carbon sphere

Functional Groups Additional elements (mostly oxygen and nitrogen) create wider variety of organic compounds Alcohols Aldehydes Amines Ester