Brooker Biology Chapter 2

Atomic nucleus

Very small volume at the center of an atom. Consists of protons and neutrons.

Electron Shells

An energy level of electrons at a characteristic average distance from the nucleus of an atom.

Radioisotopes

Unstable isotopes; they emit radiation which converts them to a stable form.

Trace elements

Elements that are present in extremely small quantities but still are essential for normal growth and function of an organism.

Compound

Molecule that is composed of two or more different elements.

Octet rule

Rule that states that many atoms are most stable when they have eight electrons in their outermost electron shell.

Nonpolar Covalent Bond

Type of a chemical bond where a pair of electrons are equally shared between two atoms; bond between atoms with similar electronegativities, such as two carbon atoms. Very strong bond.

Enzymes

Molecules found in all cells that facilitate or catalyze many biologically important chemical reactions.

Van der Waals dispersion forces

Type of weak molecular attraction that arises because electrons are located within orbitals in a random way.

Ion

If an atoms or molecule gains or loses one or more electrons, it acquires a net electric charge and becomes an ____.

Cations

Ions that have a net positive charge.

Anions

Ions that have a net negative charge.

Ionic bond

A bond that occurs when a cation binds to anion.

Free radical

A molecule containing an atom with a single, unpaired electron in its outer shell; can be charged or neutral.

Matter

Anything that contains mass and occupies space.

Atoms

Smallest functional units of matter that form all chemical substances and ultimately all organisms; cannot be further broken down into other substances by ordinary chemical or physical means.

Molecules

Two or more atoms bound together.

Element

Pure substance made up of only one kind of atom.

Proton

Positive charge, part of the atomic nucleus

Neutron

No charge, part of the atomic nucleus

Electron

Negative charge, in regions at various distances from the nucleus

Orbital

The physical region of space where an electron may be found. Can contain a maximum of two electrons.

Energy

The capacity to do work or cause change.

Valence Electrons

Electrons in the outermost shell of an atom. Allow atoms to form chemical bonds with each other, in which two or more atoms become joined together to create a new substance.

Atomic number

Number of protons in an atom.

Atomic mass

Atom's mass relative to the mass of other atoms.

Dalton (Da)

Atomic mass unit (amu); about the mass of a proton or a hydrogen atom.

Mole

A_______ of any substance contains the same number of particles as there are atoms in exactly 12 g of carbon; contains 6.02X10^23 atoms.

Isotopes

Atoms of the same element that have different numbers of neutrons.

Molecular formula

Formula that consists if the chemical symbols for all of the atoms that are present in a compound, and a subscript that tells you how many of those atoms are present in the molecule.

Covalent bond

Bond, in which atoms share a pair of electrons; can occur between atoms whose outer shells are not full.

Structural formula

A formula in which each covalent bond is represented by a line indicating a pair of shared electrons. Like H-O-H in H2O.

Double bond

Bond that occurs when atoms share two pair of electrons (four electrons) rather that one pair. O=O for O2.

Electronegativity

How strongly an atom will attract electrons from another atom in a chemical bond. ________ of an atom is a measure of its ability to attract electrons in a bond with another atom.

Polar Covalent Bond

Type of a chemical bond where a pair of electrons are unequally shared between two atoms; when two atoms with different electronegativities form a covalent bond, the shared electrons are more likely to be closer to the nucleus of the atom of higher electronegativity than to the atom of lower electronegativity. Such bonds are called______, because the distribution of electrons around the nuclei creates a polarity, or difference in electric charge, across the molecule.

Hydrogen Bond

A bond that form when a hydrogen atom from one polar molecule becomes electrically attracted to an electronegative atom, such as an oxygen or nitrogen atom, in another polar molecule. H---O; individual bond is weak.

Chemical reaction

A reaction that occurs when one or more substances are changed into other substances by making or breaking of chemical bonds; this requires source of energy (heat), these reactions need to be catalyzed, and need to reach a state of equilibrium.

Catalyst

A substance that speeds up the rate of a chemical reaction (like enzymes).

Chemical equilibrium

Chemical reactions may eventually reach ___________, in which the rate of the formation of products equals the rate of the formation of reactants, in other worlds, the concentrations of products and reactants do not change.

Solutes

Substances dissolved in a liquid

Solvent

Liquid in which solutes are dissolved

Solution

Solutes dissolve in a solvent to form a _______.

Aqueous solutions

Solutions made with water

Hydrophilic

Literally means "water-loving;" molecules that contain ionic and/or polar covalent bonds that dissolve in water.

Hydrophobic

Literally means "water-fearing;" molecules that do not have partial positive and negative charges and, therefore, are not attracted to water molecules (oils are such molecules).

Amphipathic

(from Greek for "both loves") molecules that have both hydrophilic regions and hydrophobic regions.

Micelles

When mixed with water, long amphipathic molecules may aggregate into spheres called______. Polar (hydrophilic) regions at the surface, where they are attracted to the surrounding water molecules; nonpolar (hydrophobic) ends are oriented toward the interior. (works like detergent).

Concentration

The amount of a solute dissolved in a unit volume of solution.

Molecular Mass

The sum of the atomic masses of all the atoms in the molecule.

Molarity

The number of moles of a solute dissolved in 1 L of solution.

Heat of vaporization

The heat required to vaporize 1 mole of any substance at its boiling point.

Heat of fusion

The amount of heat that must be withdrawn or released from substance to cause it to change from liquid to the solid state.

Specific heat

The amount of heat required to raise the temperature of 1 gram of a substance by 1 C

Colligative properties

Properties that depend strictly on the total number of dissolved solutes, not on the specific type of solute. (Why oceans don't freeze)

Hydrolysis reaction

Reaction in which water is used to break apart another molecule.

Cohesion

The phenomenon of water molecules attracting each other (through hydrogen-bonding properties)

Adhesion

The ability of water to be attracted to, and thus adhere to, a surface that is not electrically neutral. (lubrication)

Surface tension

A measure of the attraction between molecules at the surface of a liquid.