Chapter 2: Chemical Bonds and Reactions

activation energy

The collision energy needed to break the chemical bonds of reactants.

ionic bond

The force of attraction that holds ions with opposite charges together.

reduction

The gain of electrons; the reduced substance gains energy during the process

oxidation

The loss of electrons; process releases energy

electronegativity

The power of an atom to attract electrons to itself.

reactant

The starting substances of a chemical bond

cohesion

The tendency of like particles to stay together

polar covalent bond

Two atoms share electrons unequally; one atom attracts electrons more strongly than the other.

single covalent bond

Two atoms share one electron pair.

double covalent bond

Two atoms share two electron pairs

octet rule

Two or more atoms can interact in ways that produce chemically stable arrangements of 8 valence electrons for each atom; explains why atoms will interact in predictable ways.

surface tension

A measure of the difficulty of stretching or breaking the surface of a liquid.

anion

A negatively charged ion

endergonic reaction

Absorbs more energy than it releases

temperature

An increase causes particles to move around more rapidly; increasing the likelihood that atoms will collide.

catalyst

Chemical compounds that speed up chemical reactions by lowering the activation energy needed for a reaction to occur; also helps orient the colliding particles. Most important in the body are enzymes.

reversible reaction

Chemical reaction where the products can revert to the original reactants. ie: AB breaks down into A+B; A+B can combine to form AB.

valence shell

Contains electrons, the number of which determine if an atom will form a chemical bond with another atom. Containing 8 electrons is chemically stable and unlikely to bond with other atoms.

product

Ending substances of a chemical bond

law of conservation of energy

Energy cannot be created or destroyed; it may be converted from one form to another.

concentration

More particles of matter in a confined space; increases the likelihood that atoms will collide.

chemical reaction

Occurs when new bonds form or old bonds break between atoms. The total mass of the reactants = the total mass of the products.

exergonic reaction

Releases more energy than it absorbs

triple covalent bond

Two atoms share three electron pairs

covalent bond

Two or more atoms sharing electrons instead of gaining or losing electrons; may form between same or different elements; most common chemical bond in the body forming most of the body's structures.

non polar covalent bond

When two atoms share electrons equally; one atom does not attract electrons more strongly than the other one. Always occurs between two identical atoms.

synthesis reaction

When two or more atoms, ions or molecules combine to form new and larger molecules; collectively referred to as anabolism; usually endergonic.

cation

A positively charged ion

oxidation-reduction reaction

Always parallel; when one substance is oxidized, another is reduced at the same time.

electrolyte

An ionic compound that breaks apart into positive and negative ions.

exchange reaction

Body reactions that consist of both synthesis and decomposition.

hydrogen bond

Result from the attraction of oppositely charged parts of molecules instead of sharing electrons; weak compared to ionic and covalent bonds; cannot bind atoms into molecules

investment

Energy needed to start a chemical reaction

chemical bonds

Forces that hold together the atoms of a molecule or compound.

chemical energy

Form of potential energy that is stored in the bonds of molecules and compounds.

decomposition reaction

Split up large molecules into smaller atoms, ions or molecules; collectively referred to as catabolism; usually exergonic.