1. Matter has weight and occupies space, the simplest form of which is an element.

2. Each element can be identified by its atomic number, the number of protons in its nucleus.

3. There are 92 naturally occurring elements, six of which (O, C, H, N, Ca, and P) that account for 98.5% of the weight of the body.

4. Trace elements (Cr, Co, Cu, F, I, and Mn) play vital roles in physiology even though they make up only 0.8% of body weight.

5. The abundance of elements within the body is different than the relative quantities that occur in nature. The body is selective in its use of elements.

1. All matter is composed of atoms.

2. Atoms are made up of positively charged protons and neutral neutrons occupying the nucleus, and tiny, negatively-charged electrons in orbit around the nucleus.

3. Each proton or neutron weighs one atomic mass unit.

4. Atomic mass equals the number of protons plus the number of neutrons for an element.

5. Electrons determine the chemical properties of the atom.

6. When the number of protons and number of neutrons are equal, the atom is electrically neutral.

7. Electrons encircle the nucleus in electron shells or energy levels.

8. The innermost shell can hold up to two electrons. The outermost shell, holding the valence electrons, can have eight electrons, following the octet rule (rule of eight).

1. Isotopes vary in their number of neutrons.

2. All isotopes of the same element behave the same chemically.

3. Atomic weight considers the average mass of the atoms in a sample of an element.

1. Ions are charged particles (not electrically neutral).

2. Formation of ions is called ionization.

3. An anion has gained an electron, and thus carries an extra negative charge.

4. A cation has lost an electron, and bears a positive charge.

5. The charge of an ion is its valence.

1. Electrolytes are molecules that ionize in water, forming a solution that can conduct electricity.

2. Electrolytes are essential to nerve and muscle function.

1. A free radical contains an odd number of electrons, and tends to be reactive and destructive to other molecules.

2. Free radicals combine quickly with other molecules, converting them into free radicals, triggering chain reactions that lead to cell damage and death.

3. Antioxidants are one mechanism that neutralizes free radicals, in particular neutralizing the free radicals of oxygen.

4. Selenium and vitamin E are two dietary antioxidants.

1. Two or more atoms combined are called molecules.

2. When molecules are made up of two or more different elements, they are called compounds.

1. The simplest way of representing a molecule is by using a molecular formula.

2. Structural isomers have the same atomic compositions, but with different atomic arrangements.

3. Structural formulae are used to show the location of each atom.

1. The molecular weight (MW) of a compound is obtained by adding the atomic weights of its atoms.

1. A chemical bond is an attraction between atoms, usually to form stable valence shells.

2. Ionic bonds (p. 58; Fig. 2.7)

3. Covalent Bonds (p. 59; Figs. 2.8 - 2.10; Transps. 23, 24)

4. Hydrogen Bonds (p. 61; Fig. 2.10; Transp. 24; Table 2.4)

1. A mixture occurs when substances are physically blended together, but do not combine chemically.

1. Solutions (p. 61; Fig. 2.11)

2. Colloids (p. 62; Fig. 2.11)

3. Suspensions (p. 62; Fig. 2.11; Table 2.5)

1. Solutions are described in terms of their concentration (amount of solute in a volume of solvent).

2. Weight per Volume (p. 63)

3. Percentages (p. 63)

4. Molarity (p. 63; Table 2.6; Fig. 2.12; Transp. 25)

5. Electrolyte Concentrations (p. 64)

1. An acid is a molecule that releases a proton (hydrogen ion) in water.

2. A base is a proton acceptor.

1. Acidity is expressed as pH, a measure of the molarity of hydrogen ions.

2. pH is defined as the negative logarithm of hydrogen ion molarity.

3. A neutral solution has a pH of 7; solutions with a pH of less than 7 are acids; those with pH readings greater than 7 are bases.

4. Chemicals that resist changes in pH are buffers.

1. A chemical reaction is the process in which a chemical bond is made or broken.

2. Reactants are the substances entering reactions; products are the result of the reaction.

3. A chemical equation is a symbolic representation of a reaction.

4. According to the law of conservation of mass, no quantities are altered during a reaction, so an equation must be balanced.

1. In decomposition reactions, a larger molecule is broken down into smaller parts.

2. In synthesis reactions, two or more smaller molecules are joined to form a large one.

3. During exchange reactions, two molecules exchange groups of atoms.

1. Reversible actions can go in either direction, depending upon the abundance of reactants or products, and are represented by a two-way arrow.

2. Reversible reactions exist in equilibrium state.

1. Reaction rates are dependent upon concentration of reactants, temperature, and the presence of catalysts.

1. Work means to move something; all the body's activities are a form of work.

2. Energy is the capacity to do work. Kinetic energy is the energy of motion. Potential energy is the capacity for two stationary objects to interact.

3. Chemical energy is potential energy stored within chemical bonds.

4. Heat is the kinetic energy of molecular motion.

1. Certain isotopes are unstable (called radioisotopes), and decay to form stable isotopes. The process of decay is radioactivity, which releases radiation.

2. Radioisotopes have half-lives, the time required for 50% of its atoms to decay to a stable state.

3. There are three kinds of ionizing radiation: alpha, beta, and gamma particles, the last being the most dangerous.

4. Radiation Exposure (p. 69; Table 2.9)

1. Thermodynamics is the science of heat and energy conversions.

2. The first law of thermodynamics states that energy can be converted from one form to another, but it cannot be created or destroyed.

3. The second law of thermodynamics states that in every energy transfer, some energy is lost as heat and is no longer available to do work.

4. Free energy is the energy available in a system to do work.

5. A system's degree of disorder is called entropy.

1. Catabolism consists of energy-releasing (exergonic) decomposition reactions.

2. Anabolism consists of synthesis (endergonic) reactions that require energy input.

1. Oxidation occurs in a chemical reaction in which a molecule gives up electrons and releases free energy. Whatever took the electrons is the oxidizing agent (electron acceptor); the donor was oxidized.

2. Reduction takes place when a molecule accepts electrons. The electron donor is the reducing agent, or electron donor.

3. Oxidation and reduction always accompany one another in oxidation-reduction (redox) reactions.

CHAPTER ESSAY: Radioisotopes in Research, Diagnosis, and Therapy (p. 72; Figs. E.1 - E.3)