Bio 110 Chapter 2

organic compound

A compound consisting of a backbone made up of carbon atoms. Compare with inorganic compound.

solute

A dissolved substance. Compare with solvent.

chemical bond

A force of attraction between atoms in a compound. See covalent bond, hydrogen bond, and ionic bond.

electronegativity

A measure of an atom's attraction for electrons.

proton

A particle present in the nuclei of all atoms that has one unit of positive charge and a mass of 1 atomic mass unit (amu). Compare with electron and neutron.

anion (an'-eye-on)

A particle with one or more units of negative charge, such as a chloride ion (Cl-) or hydroxide ion (OH-). Compare with cation.

cation

A particle with one or more units of positive charge, such as a hydrogen ion (H+) or calcium ion (Ca2+). Compare with anion.

electron

A particle with one unit of negative charge and negligible mass, located outside the atomic nucleus. Compare with neutron and proton.

chemical formula

A representation of the composition of a compound; the elements are indicated by chemical symbols with subscripts to indicate their ratios. See molecular formula, structural formula, and simplest formula.

inorganic compound

A simple substance that does not contain a carbon backbone. Compare with organic compound.

acidic solution

A solution in which the concentration of hydrogen ions [H+] exceeds the concentration of hydroxide ions [OH-]. An acidic solution has a pH less than 7. Compare with basic solution and neutral solution.

basic solution

A solution in which the concentration of hydroxide ions [OH-] exceeds the concentration of hydrogen ions [H+]. A basic solution has pH greater than 7. Compare with acidic solution and neutral solution.

neutral solution

A solution of pH 7; there are equal concentrations of hydrogen ions [H+] and hydroxide ions [OH-]. Compare with acidic solution and basic solution.

matter

Anything that has mass and takes up space.

hydrophobic

Not readily interacting with water; having less affinity for water molecules than they have for each other. Compare with hydrophilic.

redox reaction (ree'-dox)

The chemical reaction in which one or more electrons are transferred from one substance (the substance that becomes oxidized) to another (the substance that becomes reduced). See oxidation and reduction.

ionization

The dissociation of a substance to yield ions, e.g., the ionization of water yields H+ and OH-.

valence electrons

The electrons in the outer electron shell, known as the valence shell, of an atom; in the formation of a chemical bond, an atom can accept electrons into its valence shell or donate or share valence electrons.

bond energy

The energy required to break a particular chemical bond.

reduction

The gain of one or more electrons (or hydrogen atoms) by an atom, ion, or molecule. Compare with oxidation.

oxidation

The loss of one or more electrons (or hydrogen atoms) by an atom, ion, or molecule. Compare with reduction.

pH

The negative logarithm of the hydrogen ion concentration of a solution (expressed as moles per liter). Neutral pH is 7, values less than 7 are acidic, and those greater than 7 are basic.

atomic number

The number of protons in the atomic nucleus of an atom, which uniquely identifies the element to which the atom corresponds.

Avogadro's number

The number of units (6.02 × 1023) present in one mole of any substance.

adhesion

The property of sticking to some other substance. Compare with cohesion.

cohesion

The property of sticking together. Compare with adhesion.

molecule

The smallest particle of a covalently bonded element or compound; two or more atoms joined by covalent bonds.

atom

The smallest quantity of an element that retains the chemical properties of that element.

molecular mass

The sum of the atomic masses of the atoms that make up a single molecule of a compound; expressed in atomic mass units (amu) or daltons.

heat

The total amount of kinetic energy in a sample of a substance.

atomic mass

The total number of protons and neutrons in an atom; expressed in atomic mass units or daltons.

radioisotopes

Unstable isotopes that spontaneously emit radiation; also called radioactive isotopes.

van der Waals interactions

Weak attractive forces between atoms; caused by interactions among fluctuating charges.

base

(1) A substance that is a hydrogen ion (proton) acceptor; bases unite with acids to form salts. Compare with acid. (2) A nitrogenous base in a nucleotide or nucleic acid. See purines and pyrimidines.

hybridization

(1) Interbreeding between members of two different taxa. (2) Interbreeding between genetically dissimilar parents. (3) In molecular biology, complementary base pairing between nucleic acid (DNA or RNA) strands from different sources.

ionic compound

A substance consisting of cations and anions, which are attracted by their opposite charges; ionic compounds do not consist of molecules. Compare with covalent compound.

buffer

A substance in a solution that tends to lessen the change in hydrogen ion concentration (pH) that otherwise would be produced by adding an acid or base.

element

A substance that cannot be changed to a simpler substance by a normal chemical reaction.

acid

A substance that is a hydrogen ion (proton) donor; acids unite with bases to form salts. Compare with base.

structural formula

A type of chemical formula that shows the spatial arrangement of the atoms in a molecule. Compare with simplest formula and molecular formula.

hydrogen bond

A weak attractive force existing between a hydrogen atom with a partial positive charge and an electronegative atom (usually oxygen or nitrogen) with a partial negative charge. Compare with covalent bond and ionic bond.

isotope (eye'-suh-tope)

An alternative form of an element with a different number of neutrons but the same number of protons and electrons. See radioisotopes.

hydroxide ion

An anion (negatively charged particle) consisting of oxygen and hydrogen; usually written OH-.

neutron (noo'-tron)

An electrically neutral particle with a mass of 1 atomic mass unit (amu) found in the atomic nucleus. Compare with proton and electron.

salt

An ionic compound consisting of an anion other than a hydroxide ion and a cation other than a hydrogen ion. A salt is formed by the reaction between an acid and a base.

polar covalent bond

Chemical bond formed by the sharing of electrons between atoms that differ in electronegativity; the end of the bond near the more electronegative atom has a partial negative charge, and the other end has a partial positive charge. Compare with nonpolar covalent bond.

nonpolar covalent bond

Chemical bond formed by the equal sharing of electrons between atoms of approximately equal electronegativity. Compare with polar covalent bond.

kinetic energy

Energy of motion. Compare with potential energy.

electron shell

Group of orbitals of electrons with similar energies.

hydrophilic

Interacting readily with water; having a greater affinity for water molecules than they have for each other. Compare with hydrophobic.

nonpolar molecule

Molecule that does not have a positively charged end and a negatively charged end; nonpolar molecules are generally insoluble in water. Compare with polar molecule.

polar molecule

Molecule that has one end with a partial positive charge and the other with a partial negative charge; polar molecules are generally soluble in water. Compare with nonpolar molecule.

orbital

Region in which electrons occur in an atom or molecule.

solvent

Substance capable of dissolving other substances. Compare with solute.

product

Substance formed by a chemical reaction. Compare with reactant.

reactant

Substance that participates in a chemical reaction. Compare with product.

chemical symbol

The abbreviation for an element; usually the first letter (or first and second letters) of the English or Latin name.

calorie

The amount of heat energy required to raise the temperature of 1 g of water 1°C; equivalent to 4.184 joules. Compare with kilocalorie.

heat of vaporization

The amount of heat energy that must be supplied to change one gram of a substance from the liquid phase to the vapor phase.

specific heat

The amount of heat energy that must be supplied to raise the temperature of 1 g of a substance 1°C.

atomic mass unit (amu)

The approximate mass of a proton or neutron; also called a dalton.

mole

The atomic mass of an element or the molecular mass of a compound, expressed in grams; one mole of any substance has 6.02 × 1023 units (Avogadro's number).

surface tension

The attraction that the molecules at the surface of a liquid may have for one another.

temperature

The average kinetic energy of the particles in a sample of a substance.

ionic bond

The chemical attraction between a cation and an anion. Compare with covalent bond and hydrogen bond.

covalent bond

The chemical bond involving shared pairs of electrons; may be single, double, or triple (with one, two, or three shared pairs of electrons, respectively). Compare with ionic bond and hydrogen bond.