Chapter 2 Definitions

Question 1

Element

Answer 1

A substance that cannot be converted to simpler substances by ordinary chemical means.

Question 2

Atomic Number

Answer 2

The number of protons in the nucleus of an atom; also equals the number of electrons around the neutral atom. Determines the chemical properties of the atom.

Question 3

Electron Shell

Answer 3

The region surrounding the atomic nucleus at a fixed energy level in which electrons orbit.

Question 4

Molecule

Answer 4

A chemical substance made up of two or more atoms joined by covalent bonds or ionic attractions.

Question 5

Ionic Bond

Answer 5

An electrostatic attraction between positively and negatively charged ions.

Question 6

Anion

Answer 6

A negatively charged ion. (Contrast with cation.)

Question 7

Cation

Answer 7

An ion with one or more positive charges. (Contrast with anion.)

Question 8

Covalent Bond

Answer 8

Chemical bond based on the sharing of electrons between two atoms.

Question 9

Electronegativity

Answer 9

The tendency of an atom to attract electrons when it occurs as part of a compound.

Question 10

Polar Covalent Bond

Answer 10

A covalent bond in which the electrons are drawn to one nucleus more than the other, resulting in an unequal distribution of charge.

Question 11

Hydrogen Bond

Answer 11

A weak electrostatic bond which arises from the attraction between the slight positive charge on a hydrogen atom and a slight negative charge on a nearby oxygen or nitrogen atom.

Question 12

Heat of Vaporization

Answer 12

The energy that must be supplied to convert a molecule from a liquid to a gas at its boiling point.

Question 13

Hydrophillic

Answer 13

Having an affinity for water. (Contrast with hydrophobic.)

[Gk. hydro: water + philia: love]

Question 14

Hydrophobic

Answer 14

Having no affinity for water. Uncharged and nonpolar groups of atoms are hydrophobic. (Contrast with hydrophilic.)
[Gk. hydro: water + phobia: fear]

Question 15

Cohesion

Answer 15

The tendency of molecules (or any substances) to stick together.

Question 16

Functional Group

Answer 16

A characteristic combination of atoms that contribute specific properties when attached to larger molecules.

Question 17

Macromolucule

Answer 17

A giant (molecular weight > 1,000) polymeric molecule. The macromolecules are the proteins, polysaccharides, and nucleic acids.

Question 18

Polymer

Answer 18

A large molecule made up of similar or identical subunits called monomers. (Contrast with monomer.)

Question 19

Monomer

Answer 19

A small molecule, two or more of which can be combined to form oligomers (consisting of a few monomers) or polymers (consisting of many monomers).

Question 20

Saturated fatty acid

Answer 20

A fatty acid in which all the bonds between carbon atoms in the hydrocarbon chain are single bonds—that is, all the bonds are saturated with hydrogen atoms. (Contrast with unsaturated fatty acid.)

Question 21

Unsaturated fatty acid

Answer 21

A fatty acid whose hydrocarbon chain contains one or more double bonds. (Contrast with saturated fatty acid.)

Question 22

Hydrolysis

Answer 22

A chemical reaction that breaks a bond by inserting the components of water (AB + H2O → AH + BOH). (Contrast with condensation reaction.)

Question 23

Condensation

Answer 23

A chemical reaction in which two molecules become connected by a covalent bond and a molecule of water is released (AH + BOH → AB + H2O.) (Contrast with hydrolysis reaction.)